The disclosed passive substrate for switch power module comprises: a passive substrate layer with a magnetic core and corresponding top and bottom winding layer, and a circuit layer. Wherein, the magnetic core is embedded in the board, the winding layers connect with each other through an interconnection hole, and an insulation layer contained epoxy resin and glass fiber isolates the winding layer and magnetic core. This invention simplifies design and manufacture for power module, reduces cost, and increases power density for the switch power module greatly.