I want to join Amity University on jee main basis so what should be the good score in jee mains to get admission in Amity University

Amity University have 9 campuses ; 3 in UP, one each in Rajasthan, Maharashtra, Chhattisgarh,  Madhya Pradesh, West bengal & Haryana.

and these institutes will take admission admission through CSAB counselling based on JEE Main Rank.
Cut off will vary for each campus and branch.

You should try to score more than 90 marks in JEE Main to get admission in Amity, Noida.

Good Luck.