The invention relates to a double-sealing-structure type flat gate valve. The double-sealing-structure type flat gate valve comprises a valve body, a valve cover which is connected to the upper end ofthe valve body, and a valve rod which is in match with the valve cover, wherein the upper end of the valve rod extends out of the valve cover to be in fitting connection with a performer assembly, and the lower end of the valve rod extends into a chamber of the valve body to be connected to a gate plate; an upstream channel at the left side of the valve body and a downstream channel at the rightside of the valve body communicate with the middle part of the valve chamber; a tubular upstream valve seat is arranged at the part where the upstream channel is connected to the valve chamber; a tubular downstream valve seat is arranged at the part where the downstream channel is connected to the valve chamber; the gate plate is positioned between the upstream valve seat and the downstream valveseat; an upstream sealing structure is arranged at the part where the upstream valve seat is connected to the upstream channel; a downstream sealing structure which is the same as the upstream sealingstructure is arranged at the part where the downstream valve seat is connected to the downstream channel. The double-sealing-structure type flat gate valve is high in reliability, long in service life, free from maintenance, and applicable to harsh working conditions such as underwater oil and gas production.