can dog understand peoples language?

Well, I can't speak for all dogs, but I know my dog understands many things. He knows "NO", "DOWN" "GO FOR A WALK", "GO TO THE PARK", "NITE-NITE", "BAD"... Once he understands a word or phrase he doesn't forget it.

dog cant understand language of people but they have some amazing sense which dont have human.

Cute Q, and I suggest that even human scientists can't accurately answer. Certainly an animal can detect "Words" or phrases that the LEARN in an association with an occurance or event, IE: "Wanna go for a walk?" On the humorous side however, and especially with cats, I like to think of their interpretations this way. As a pet owner one often "talks" to their particular pet, perhaps sometimes scolding them. I like to think that they hear this "BAD DOG, why did you tear up my slippers?" AS THIS, "BLAH,BLAH,BLAH,BLAH",,,SMILES Steven Wolf

i dont actually think dogs understand words per say.. i do believe that the understand by the tone of your voice.. the hand gestures and/or body language you use when speaking to them.. or the actions u take.. for example.. when u say "wanna go outside' in an excited voice and open the door.. when u do that a few times for them.. anytime you say 'wanna go outside' in that same voice.. in a different room from where the door is.. your dog will automatically go to the door and wait for u to open it..

I very much believe that dogs understand us. However, I don't think it's only verbal language that dogs respond to, also body language and tone. I believe it's a combination of those things that dogs react to. Certainly, we know that dogs can learn words in some way. However, if you don't have the tone (generally a higher pitch if positive, or lower tone if negative), I've found that dogs don't always respond as you want them to.