Well,i need to learn how to change blonde long hair to black with photoshop.I tried to make it with mask tool and then i used changing the color but that didn't gives me the black.Please help me...

It would be helpful if you upload the image. See link below my signature. I'm sure someone will be able to make suggestions.

It could depend how blonde the hair is but you could try duplicating the layer and inverting it and use a layer mask to show only the dark hair. Probably worth playing with the blend modes as well.

As Danny says if you post a picture you will get more specific help.

Christine