Abstract: Aiming at the particularity of Francis turbine runner's simulation in the process of welding, the method was adopted which solved the loading of welding thermal source by means of node-to-node connection and the method was brought forward which solved the problem of weld's wire feed by dividing the weld into many parts. These two methods were proved reasonably by the runner's temperature field. Moreover, the problem of heat conduction between independent entities and the problem of heat elimination between blade and air were successfully solved by using contact bodies. It had important guiding significance to the numerical simulation of complicated weldments.