How do I get my 3yr old son not to b scared of the dog

My son is scared of our dog he has never had no bad experience with any animals, we had this dog from a puppy n now 9 months old

Recently, our city's PAL Humane Society held a Camp Kindness.  It taught my daughter about dogs and how to interact with them properly.  They also taught her what not to do with dogs.  I think if you found something like that for him to do, it might help. 

I have found that interaction with animals is the best thing to help with their fears. 

Maybe the puppies energetic activities are overwhelming for your son. Sometimes the overstimulation can cause anxiety in kids, and it just takes time to adjust. Understand that your puppy is in the "terrible twos" stage and is probably a lot more active than it was a few months ago.

I also have to agree with the response about the PAL camp, finding activities like that are helpful with situations like yours. They have simular activities at Petsmart also.

Good Luck!