enage the bully yourself by playing with him. Talk to him. Chat with him. KNOW HIS NAME AND SAY HI TO HIM WITH HIS NAME. Little kids just want attention. The more you are engaged with him and with the rest of the kids in the playground, they are more aware of the "power" your daughter has.
That is why many parents are engaged in the Teach Parent Association. The more engaging you are, the more presence you have with the school and with other parents (and sure enough they will talk about you and your family's invovlment with their kids), the more your kids are treated nicely and fairly in school. You are part of the scene, part of the game and part of the establishement.
Unfortunately many Chinese parents are unwilling to sacrifice their free time to be invovlved with the school, with teachers, with other kids and their parents. And at the end, your kid ends up being left out.
So start with THIS BULLYING KID. Engage him nicely. Start with knowing his name and make conversation with him at the first name basis. And YOUR KID WILL WATCH AND LEARN.