The invention discloses a warm extrusion method and a mould for a continuous equal-square channel with a pre-stress structure. The structural characteristics are that a reversed-bell-shaped double-layered combined concave mould pre-stress structure is adopted so that not only can mould materials be utilized effectively, but the bearing capability can also be guaranteed. The warm extrusion method comprises the following steps: analyzing a warm extrusion process of the continuous equal-square channel through finite elements by a continuous equal-square channel to obtain an optimized mould geometrical shape and a technological parameter; designing a warm extrusion experiment mould of the continuous equal-square channel according to basic requirements of low-carbon steel extrusion and molding; and improving a regular structure of a concave mould. The strength and the service life of a convex mould are not only considered in the aspect of the used materials, but also are guaranteed in the aspect of the structural design of the convex mould. With the adoption of the warm extrusion method and mould, the concave mould can be effectively prevented from being fractured; the service life of the mould is prolonged and the efficiency of experiment researches is improved; the time and the money are saved.