sir,I got 99.9450358 percentile in jeemains January 2020.which colleges ,can I get for doing B.TECH CSE .

Hello.
At 99.9450358 percentile in JEE mains your approximate rank would be 478 ( if I consider for general category) which is under 500 which is a very good rank and you have decent chances of admission in all 31 NIT in Computer science and Engineering branch some of these are listed below:

• NIT tiruchirappalli.
• NIT Warangal.
• NIT Jalandhar.
• NIT Jaipur.
• NIT Allahabad.
• NIT Agartala.
• NIT arunachal Pradesh.
• NIT Calicut.

Now it would be a wise decision if you will appear for JEE advanced at this percentile you are definitely qualified for JEE advanced.
Now if you want to know more colleges with this percentile then you can use our college predictor tool from the below link:

JEE Main College Predictor 2020 - Predict Colleges based on your JEE Main Rank

JEE Main College Predictor – Know your College Admission Chances Based on your Rank/Percentile, Home State, Caste, Gender, Exam Result & Get ...

Best of luck.

Congratulations for getting such good marks. As you got 99.9450358 percentile in the January Session, your expected rank will be under 500. At this rank you can easily get CSE in top NITs such Trichy, Warangal, Surathkal, Rourkela. Or it will be better if you appear for Jee Advanced, qualify it with good marks and get into IITs. Though you can check NITs previous years' cutoff here-
http://engineering.careers360.com/articles/nits-cutoff-for-top-btech-branches