The invention provides a combined die for a concrete sample and a manual demoulding device. The combined die comprises a steel external overall die and a plastic slidable base plate. The manual demoulding device matched with the combined die comprises a rubber base plate, a bearing column, a bearing steel plate, a pressing-down devices, pinions, bull gears, telescopic pressing rods, a base, tenons and preserved holes. The bearing column with the rubber base plate embedded in the top is vertically mounted on the base. The die pressing-down devices capable of adjusting horizontal positions are arranged at colinear symmetrical positions on two sides of the bearing column, and the pressing-down devices are positioned through the tenons and the preserved holes so as to adapt to the demoulding of concrete samples of different sizes. The manual demoulding device has the advantages that by pressing down pressing rods, the sample can be separated from the die under force transmitted by the gears; the sample can be conveniently and fast separated from the die without being damaged, and the manual demoulding device is little in application site limitation, convenient in manual demoulding and capable of increasing sample utilization rate.