You might wanna try Verium. It's CPU only and GPUs can't be used to mine this coin. The only problem is the minimum withdrawal on pools. You may have to wait for months before you receive your first payment unless you have a CPU farm. You can also Solo mine Verium but it seems the difficulty is a little too much.
As others said, Cryptonight is one of the best algos for CPU mining as GPUs do not have too much advantage over decent CPUs, especially the AMD ones. Look for Cryptonote coins with less network hashrate and mine them.
where can i find those coins? can you teach me , i am a newbie ,thank you very much As others said, Cryptonight is one of the best algos for CPU mining as GPUs do not have too much advantage over decent CPUs, especially the AMD ones. Look for Cryptonote coins with less network hashrate and mine them.
. just because a GPU has the higher speed doesn't mean its the most efficient, unless of course you are somehow exploiting ways to get free electricity or basically stealing electricity, because there is really no such thing as free electricity. And a vega cost more or double the price of a 1070. you can almost get 2 1070 for the price of a vega. 
CPU mining is a gamble, one has to hope for the coin to move up alot in price to get bang for the electricity used. its kinda not worth it.