Hi balwan singh,

The normal eligibility criteria for doign B.Sc. Math Honours degree course is a pass degree in 10+2 or equivalent examination in Science stream with at least 50% marks obtained by candidates in Mathematics subject or in aggregate from a recognized board or Institute. 

So you need to be science stydent in class 12(non medical or both biology and maths) and score a minimum of 50% in maths or in agrregate. Hope you are clear with it.