The invention discloses a rotor composite yarn spinning device. An air extracting type spinning cup on an existing rotor yarn spinning machine can be easily abraded, and winding fibers can be easily generated during a spinning process. According to the rotor composite yarn spinning device, two feeding carding mechanisms are symmetrically arranged on the two sides of a condensation twisting mechanism, two ring-shaped condensation grooves are formed in a spinning cup, a filament guiding pipe and the spinning cup are fixed, a yarn guiding pipe and an air extracting device are fixed, a twisting stopping disc and the yarn guiding pipe are fixed, feeding openings are formed in the outer sides of the shell bodies of the two feeding carding mechanisms, the inner sides of the shell bodies of the two feeding carding mechanisms are respectively communicated with one end of a fiber conveying pipe, the other ends of the two fiber conveying pipes extend into the spinning cup, impurity discharging openings are formed in the portions, close to the corresponding fiber conveying pipes, of the two shell bodies, feeding rollers and the carding rollers are arranged in the shell bodies, the feeding rollers are arranged at the feeding openings, and feeding plates are arranged between the feeding rollers and the shell bodies. According to the rotor composite yarn spinning device, the types of the composite yarn which can be spun by a rotor yarn spinning machine can be increased, the winding fibers can be prevented from being generated, and yarn strength is improved.