The invention relates to a demolding method for a crust PP foamed sheet in a continuous extrusion die. The demolding method comprises the following steps: an extruded melt is adjusted by a high temperature channel to keep the temperature of the contact surface of the melt and an enhanced crystallization foaming device be equal to or more than 220 DEG C, the surface of the melt rapidly crusts afterthe melt reaches heat insulation holes due to the internal temperature, being 80 DEG C, of the enhanced crystallization foaming device, the enhanced crystallization foaming devices starts from the first level, cold water is introduced to make the contact surface of the device and the melt less than the crystallization temperature of PP in order to make the surface of the PP melt crystallize and crust, the surface of the PP melt is in contact with the upper surface and the lower surface of a differential crusting device to make the melt rapidly crystallized and cure pores, and a sheet which ispre-sized after conversion and crystallization of the melt is continuously defoamed and demolded under a constant pressure, leaves the differential crusting device, is continuously demolded, enters afixing die, and is fixed to obtain a qualified product. The method effectively reduce the vacuum adsorption force and other demolding resistances, facilitates the strength enhancement of a PP crystallized crusted layer, converts extrusion thrust into demolding thrust, and achieves the smooth realization of continuous crystallizing, crushing, extruding and demolding of the PP in a differential enhancement device.