I have 2 cats a 3 year old and a year old cat. The 3 year old cat just sees the other cat and follows him then when he really gets mad he attacks the cat and this has been going on for a month what should I do?

Tell us a little about them.
Was the 1 yr old raised with the other cat?
Are they both neutered?
Are they indoor cats only?

No the one year old cat was given to us by a friend but they were friendly for a while but I don't know they changed. The cats are always inside and there not neutered

Not being neutered is a huge problem.. you really need to have both of them fixed. That should cut down on the aggression a lot. When they smell a female in heat or other cats outside it will be worse. One is always going to be a little bossy over the other. But it will get only get worse if you don't get them neutered.

If they are both males then they will fight for seniority - especially the more aggressive of the two. My cat, Mouse, likes to dominate and just for fun will jump my more docile male cat, Morty, for no reason. They are not related either so that makes it worse. A firm, "no" will help - and also you might want to get a small water pistol to spray if he keeps it up. Letting them go outside for a while helps reduce the aggression. But yes, you do need to get them fixed and make sure they get their shots. Take care.