My dog's penis is bleeding and I don't know the exact reason of this and I too don't know what is the proper care of this .

It would be best to take him to the vet. Let them find the cause and show you how to care for him.

I totally agree with Cat, it's time to see the vet. They will preform a urinalysis and urine culture to make sure it's not a urinary tract infection, if no infection shows up they usually do some X rays to see if bladder stones may be the cause. They will also check his prostate and the kidneys to look for unusual marks or tumors. If your dog is not neutered, the most usual cause for this is prostate gland issues. Just another reason why neutering is so important. If it is the prostate, then neutering is usually the easiest fix. The dog will stop producing testosterone and the prostate will shrink. They will also run some blood tests to check on your dogs blood clotting abilities.