Bonsai tree care is a hobby for some and a passion for others. It takes a long time to grow the trees and form them into the varying positions that you want. The forming seems to be never ending and constantly changing as the tree spreads. If you aren't careful, it is possible to break or damage a branch while bending it into the position you want. When this happens, you might be able to repair the damage, depending on its severity.
Pull the broken branch back together, if it is still attached. Drop a little super glue in the split area of the branch to hold it together while it heals. Hold the branch until the glue dries. The glue works to keep the new branch intact until new growth can form.
Wrap wire around the split area to hold the branch together until it heals. Wrap it tightly so that the two halves of the branch will be touching. Leave the wire in place for support until it has grown back.
Clip off the damaged branch to make it a clean cut where the damage was done. Do this if the branch was completely broken off. There is no good way to get a branch that breaks in two to grow back. It will be weak, and will more than likely break again. It is best to prune it and let it grow back.