Instructions
Determine if the skittish cat is afraid just of the dog, or of people and other animals as well. This could indicate a history of abuse or neglect, and will require plenty of loving care to cure.
Separate the cat and dog so you can work with them in controlled circumstances. Continuing a pattern of fear will only exacerbate the situation, and make the fear more ingrained. Putting them in separate rooms should be sufficient.
Place the dog on a leash, and re-introduce the skittish cat and the dog in a controlled environment. It is sometimes best to do this outside of the home so that neither animal feels territorial, such as at a trainer's office or even just in the yard.
Comfort the cat while you allow the animals to sniff one another. If the cat tries to scramble away, separate the animals again and attempt to calm the cat. Then try again.
Reprimand the dog for barking or making any aggressive movements toward the cat. This behavior will have to stop if you want the two animals to live in harmony.
Place the skittish cat and the dog in separate rooms, but allow them to see one another when you are away. Childproof fences are excellent for this purpose as long as the cat can't scale the barrier.
Give treats to both the cat and dog when they get along nicely in your presence. Encourage them to either play together or at least to co-exist in harmony. Rewards are the best way to accomplish this task.
Feed the animals in separate rooms so that the skittish cat is not afraid that the dog will steal its food. This is a common source of animosity and fear, and should be eliminated.
How to Train a Very Skittish Cat to Not Be So Afraid of a Dog
Cats and dogs are notoriously incapable of getting along, but stories of scratching their canine companions on the nose are more common than stories of cats being afraid. If you have a very skittish cat that is afraid of your dog, it is important to work with both animals so that they can get along.