A sample feeding device for a trace detector, comprising: a sample feeding chamber disposed in the sample feeding device to desorb a sample from a sample feeding member; and a valve assembly, wherein the valve assembly comprises a sealing member; and a flange disposed on an inner wall of the sample feeding chamber, characterized in that the flange divides the sample feeding chamber into a first sample feeding chamber and a second sample feeding chamber, wherein the first sample feeding chamber is configured to be in fluid communication with the trace detector and the second sample feeding chamber is configured to desorb the sample from the sample feeding member, and wherein the first sample feeding chamber fluidly communicates with the second sample feeding chamber by separating the sealing member from the flange and the first sample feeding chamber is isolated from the second sample feeding chamber by bringing the sealing member into contact with the flange, the sample feeding device further comprising a sample feeding port in communication with the second sample feeding chamber, and an actuating member configured to move the sealing member to fluidly communicate the first sample feeding chamber with the second sample feeding chamber or to isolate the first sample feeding chamber from the second sample feeding chamber, the actuating member comprises: a carriage having opposite outer walls substantially parallel to each other; and slide rods disposed on the outer walls, the carriage being connected with the sealing member; and an actuating frame having grooves in which the slide rods are slideably disposed, and thereby when the actuating frame moves, the carriage is actuated to move by cooperation of the slide rods and the grooves so as to move the sealing member. a sample feeding chamber disposed in the sample feeding device to desorb a sample from a sample feeding member; and a valve assembly, wherein the valve assembly comprises a sealing member; and a flange disposed on an inner wall of the sample feeding chamber, characterized in that the flange divides the sample feeding chamber into a first sample feeding chamber and a second sample feeding chamber, wherein the first sample feeding chamber is configured to be in fluid communication with the trace detector and the second sample feeding chamber is configured to desorb the sample from the sample feeding member, and wherein the first sample feeding chamber fluidly communicates with the second sample feeding chamber by separating the sealing member from the flange and the first sample feeding chamber is isolated from the second sample feeding chamber by bringing the sealing member into contact with the flange, the sample feeding device further comprising a sample feeding port in communication with the second sample feeding chamber, and an actuating member configured to move the sealing member to fluidly communicate the first sample feeding chamber with the second sample feeding chamber or to isolate the first sample feeding chamber from the second sample feeding chamber, the actuating member comprises: a carriage having opposite outer walls substantially parallel to each other; and slide rods disposed on the outer walls, the carriage being connected with the sealing member; and an actuating frame having grooves in which the slide rods are slideably disposed, and thereby when the actuating frame moves, the carriage is actuated to move by cooperation of the slide rods and the grooves so as to move the sealing member. a carriage having opposite outer walls substantially parallel to each other; and slide rods disposed on the outer walls, the carriage being connected with the sealing member; and an actuating frame having grooves in which the slide rods are slideably disposed, and thereby when the actuating frame moves, the carriage is actuated to move by cooperation of the slide rods and the grooves so as to move the sealing member.