If I do not agree to it is it considered quiting?

Yes he can cut your salary. In most cases he could also terminate you for no reason if you are an "at will" employee. If you do not agree and fail to perform your duties it is not quittng but you could just be terminated.

I Have a contract, yes they can terminate me at anytime but must pay me one year salary. Now if they try to cut my salary do I have to agree to it and if I do not agree to it is that considered quitting? I have to be terminated to get the years salary?

It would have been beneficial to mention the contract in your first post, you are not an at will employee. I'd have to read every word of your contract to say anything more.

They and you are bound by the contract, They can not fire you for refusing to agree to terms of a new contract.
But I am sure they can find a dozen of other things to fire you for ( perhaps)

But you and them can not change the terms of the contract without both sides agreement.

So you can refuse, and they will fire you, then you sue them under any protection the contract gives you ? What penalty for them breaking the contract is there ?

And of course after you sue them, where and what job chances at other places are there?

What does the contract say? How do you expect us to give you a good answer when you don't give us the info we need to make a judgment?

The contract rules in such a situation. If the contract states unequivocally, that you will be paid x amount for x time, then no, they cannot change that without your consent. However, the contract may give them the right to terminate the contract for a variety of reasons. They may decide that if you don't agree to a new contract, they will exercise one of those reasons.

You need to sit down with that contract and read it very carefully to understand what they can and can't do and what your rights are.