For aliphatic diisocyanates, like HDI, IPDI (often the best candidate of aliphatic diisocyanates), hydrogenated MDI or TMXDI the best catalyst is DBTL which can be applied in amounts of  200-1000 ppm. Tin dilaurate, Desmorapid SO, is the best catalyst for aromatic diisocyanates like TDI or MDI. Bismuth neodecanoate can be used for all isocyanates in amounts of at least 1000 ppm but has the advantage that it is less sensitive against water, because it catalyses the reaction of isocyanate and alcohol faster than the reaction between isocyanate and water. For better dosage the catalyst can be thinned in THF as already explained by Jatin Sethi. High amounts of catalysts have no negative influence on the polyaddition reaction itself but on the stability of the resulting polyurethane. DMSO and NMP are not optimal in PU formation because they are not "innocent" solvents. They can also react with the diisocyanate. They should only be applied if the diol component is not soluble in other solvents. THF is in most cases the best solvent for PU reaction, but also MEK - and if the solubility of the diol allows it - halogenated hydrocarbons, esters or aromatic solvents are appropriate. The concentration of reactants and polymer can be in the range of 25 %. The stoichiometry should be near 1:1. In several cases a slight isocyanate excess of 1% could be advantageously. Dryness of the diol and the solvent is crucial for a good urethane formation, because water destroys isocyanate under CO2 evolution (Bi catalyst better than Sn in respect to the water reaction but less active). 

The monomer mol. should be equal that is one point. You and carry the reaction in low temperature 60 oC or less than that. Reg. solvent if the monomers are soluble in THF then you can use dry THF or Toluene as the solvent.  Reg. isocyanate you can try with IPDI comparing with TDI or MDI. IPDI reactivity ratio is slow so that you will get linear polymer. The reaction should be moisture free.

It you want a linear polymer, you should only use bifunctional monomers (dipolyol and diosocyanate). Remember to vaccum dry the polyol as water can react with isocyanate and screw up your stoichometry. The ratio as others have mentioned (1:1) is correct. If even one drop of catalyst is too much, you can make 10% solution in THF and in that way you will be able to add precise amount needed. Good Luck!

So could I know that if too much catalyst DBTDL added in the polymerization-condition，is there any bad consequence for the polymerization？

For aliphatic diisocyanates, like HDI, IPDI (often the best candidate of aliphatic diisocyanates), hydrogenated MDI or TMXDI the best catalyst is DBTL which can be applied in amounts of  200-1000 ppm. Tin dilaurate, Desmorapid SO, is the best catalyst for aromatic diisocyanates like TDI or MDI. Bismuth neodecanoate can be used for all isocyanates in amounts of at least 1000 ppm but has the advantage that it is less sensitive against water, because it catalyses the reaction of isocyanate and alcohol faster than the reaction between isocyanate and water. For better dosage the catalyst can be thinned in THF as already explained by Jatin Sethi. High amounts of catalysts have no negative influence on the polyaddition reaction itself but on the stability of the resulting polyurethane. DMSO and NMP are not optimal in PU formation because they are not "innocent" solvents. They can also react with the diisocyanate. They should only be applied if the diol component is not soluble in other solvents. THF is in most cases the best solvent for PU reaction, but also MEK - and if the solubility of the diol allows it - halogenated hydrocarbons, esters or aromatic solvents are appropriate. The concentration of reactants and polymer can be in the range of 25 %. The stoichiometry should be near 1:1. In several cases a slight isocyanate excess of 1% could be advantageously. Dryness of the diol and the solvent is crucial for a good urethane formation, because water destroys isocyanate under CO2 evolution (Bi catalyst better than Sn in respect to the water reaction but less active).