Flat gate valve with compound seal valve seat structure

The invention relates to a flat gate valve with a compound seal valve seat structure. The flat gate valve comprises a valve body, a gate segment, a valve cover, a valve seat seal assembly and a valverod; the valve cover is fixedly connected with the valve body; the gate segment is arranged in the valve body and is in seal fit with the valve seat seal assembly; the valve seat seal assembly comprises a valve seat body, a seal pressing ring, a primary seal ring and a secondary seal ring; the seal pressing ring, the primary seal ring and the secondary seal ring are installed on the valve seat body; the seal pressing ring, the primary seal ring and the secondary seal ring are sequentially arranged from a medium channel to the outside; the primary seal ring is compacted in an annular hole of the valve seat body by the seal pressing ring; the bulged end of the seal pressing ring is flush with that of the secondary seal ring; the bulged end of the primary seal is higher than that of the sealpressing ring; and the pri