The invention discloses a comb tooth capacitive micro-electromechanical accelerometer structure. The structure comprises comb tooth groups, a mass block, flexible beams, flexible beam support rods andcomb tooth support rods, wherein the mass block is a frame structure shaped like a Chinese character Ri; the comb tooth groups are variable-gap comb tooth groups; each comb tooth for forming the combtooth groups is a pentagonal comb tooth with a gradually varied comb tooth width at the overlapped area; the comb tooth groups are crossly distributed in the inner and outer sides of the mass block frame to form a differential capacitor; the movable comb teeth of the comb tooth groups are connected with the mass block and are suspended at two ends of the flexible beam support rods on the two outermost sides of the structure through four flexible beams at four corners of the mass block frame; and the fixed comb teeth of the comb tooth groups are connected with the comb tooth support rods. Thepentagonal comb teeth is capable of increasing the tooth pair number while keeping the tooth clearance ratio, so that benefit is brought to improve the sensitivity of the accelerometer. The crossly distributed comb tooth groups are capable of making up the capacitive differences caused by nonuniform etching process so as to improve the capacitive symmetry, and is also capable of compensating the influences, on the differential capacitor, caused by environment temperature change so as to improve the stability of a calibration factor of the accelerometer.