Because big dogs can be intimidating, some small dogs might be a little fearful of your big guy. Big dogs also don't always know their size. Big dogs will try to fit into small spaces thinking that is their size, and big dogs will try to play the same way small dogs play, not truly understanding the size difference between the two. This could also mean your big dog plays a little rougher and your little guy could become injured or even stepped on.
Training your big dog to get along with a small dog is imperative, especially if you have big and small dogs in your household. They should be able to get along. They should be friends. And hopefully, if you play your cards right, they should play together too.
Training your big dog to get along with your small dog will also include training your small dog to get along with your big dog. Some small dogs are definitely bigger than their bite and can stand on their own, but others are timid, shy, and fearful. This demeanor may encourage your big dog even more. Put these two dogs on the same level when you are training them both and work with them at the same time. Be sure to offer both a treat at the same time if possible. If you give one dog a treat, be sure to give the other dog a treat. This will teach the two dogs that they are both equal in the household.
You will need lots of tasty treats to train your dogs to play together and be nice to one another. You will also need patience and training time with a big dog and a small dog. If you don't own both big dogs and small dogs, but you still want them to get along, try to find a small dog that you can introduce your big guy to, so he knows that there are dogs of all sizes out in his world and he needs to know how to interact with them. You can do this by organizing play dates through your groomer or veterinarian, or you can take your dog to a dog park and see if anyone is interested in introducing their little guy to your big guy. Be sure to have treats for both dogs at all times.