Hi, I have understood that you in trouble with a site-directed mutagenesis but please the next time specificy the experiment that you are performing.

Next we need to know what you want to do with this experiment. Do you want to mutate an aminoacid in a protein-coding construct or you are trying to delete or insert aminoacids? If you are finding the frame-shift mutation near the nucleotide that you want modify probably it's because it is contained in the primer used for the mutagenesis..please double check your primers.

I made mutation from one amino acid to another amino acid. mutation happened. but extra few unwanted amino acids are also there. I tried many times , but every time same result.

Perfect primers and enzyme to avoid frameshift mutation:

1. PFU turbo DNA polymerase (an error rate of 1.6 × 106) 

2. design specific primers : http://www.genomics.agilent.com/primerDesignProgram.jsp

Good luck

I used phusion enzyme and other two mutations worked in it. Checked primers and seems good.

From what you say It seems that your primers are degradated or not synthetized correctly.... maybe you can re-order them