Hi Kalpana, In today's scenario almost every college has its own entrance exam or the admissions are based on your performance in JEE MAINS & then Advance exam mainly for B.tech.  There are some state based colleges which give admission to students on the basis of class XII result.  Candidate must note that the admission to the State based colleges may be subject to domicile regulations giving preference to the state candidates.  Here are some State based colleges which give admission on the basis of class XII :
ANNA UNIVERSITY
It is a public state university located in Tamil Nadu, India. And the admission process is called to be TNEA ( Tamil Nadu engineering admission).
TNEA 2020 Application Form will be available from the 1st week of May 2020.
Eligibility criteria involves :

1. Candidates must have passed their 10+2 or equivalent examination from a recognized board.
2. Physics, Chemistry, and Mathematics are compulsory subjects in the qualifying examination.
3. Candidates must have scored a minimum of 50% marks (General category), 45% marks (OBC category) and 40% marks (SC, ST, SCA, MBC, DNC category) in PCM.

Rajasthan Technical University (RTU)
It  is an affiliating university in Kota in the state of Rajasthan, India.
Rajasthan Engineering Admission Process is responsible for the admissions in RTU.
Admissions are made through counseling based on rank obtained in JEE Mains
Seat vacant after JEE Mains counseling are filled on merit basis in 10+2. So this can be a good opportunity for those students who didnt score good in JEE mains or those who missed the exam.
SASTRA  University
Sastra Deemed University or the Shanmugha Arts, Science, Technology and Research Academy is a highly-ranked higher education institution in Thirumalaisamudram village of Tamil Nadu.
70% seats are filled through university level counselling based on marks obtained in class 10+2 and rank obtained in JEE Mains.
Selection parameter and weightages:
10+2 marks - 75%
JEE Mains - 25%
Remaining 30% seats are filled by the university based on the marks obtained in class 10+2.

Other than these 3 universities , MP B.Tech admission and Punjab B.Tech admission are some good options for admission in B.tech after XII.
Else there are certain private colleges such as NIIT University , Thapar University ,etc. for admission in b.tech after XII.