Sets up the reflow soldering machine dynamic model based on heat balance mechanism. According to the characteristics of high-order and strong couple, adopts the Padé interpolation technique to simplify all channels' transfer functions into second-order classic system. Designs the decoupling compensations for the system with the invariance principle, and the simulation results show that any zone temperature control is no longer influenced by other zones' temperature changes. It achieves a more precise control requirement.