How Come My Dog Want Urinate When I Take Him Outside?

A few more details might help. Did you just get the dog? Exercise stimulates elimination. Take him out and walk, walk, walk. They can only walk and hold it so long. When nature finally has its way, lavish praise on him. I frequently use that technique before taking a puppy in a public place.

You gave him too much water.

Take your dog to places where other dogs have urinated, trees fence posts, fire hydrants etc...after he has been excersized, the smell of another dogs markings will elicit the response you seek.