Your spectra are made with the sample in to high concentration. The fluctuation in the higher absorbance range is due to electronic noise that occur as you are measuring a very small fraction of the light penetrating the sample.

You should dilute your samples 2-3-fold so the highest absorbance is not more than 3.0 abs and take the spectras again.

Sir, these are the UV DRS spectras of solid samples, where samples are taken directly. I just want to know to find out absorbance value for bandgap calculation. Please help me if you know.

You need to find a way to get less sample into the photometer. If it is a solid you should cut a thinner slice or dissolve it in a solvent to make a solution.

Sir its a powdered solid. I may request you to see the procedure to take uv drs spectra. the powder is to be filled in the pellete given. its not like less or more powder nor its to make solution.

If your procedure doesn't work for the problem and you are not willing to change it you cannot be an experimental scientist.

It is true I don't know the DRS UV procedure, but it is clear from the spectra that you need to find a way to make the maximal absorbance in your spectra less than  about 3-4 to see the spectra well. The problem is essentially that if the absorbance is 6 the light intensity measured in the machine is 1 in a million of the intensity it is designed for.

I guess you can mix the sample with a powder that doesn't absorbe light.

Another method could be to increase the time the sensor reads. Make the scanning time much higher or combine (average) many spectra read from the same sample.

As Mr Anderson said, to take UV of solid sample, there is always a reference powder provided by the supplier; eg. BaSO4/ KBr etc. Mix the sample powder with the reference but in a lesser quantity. Hope you get success ASAP.