The utility model discloses a low-cost bipolar current instruction signal generating circuit. Two unipolar PWM (Pulse Width Modulation) signals are respectively connected with the input end of an electrical isolation circuit; two outputs of the electrical isolation circuit are respectively connected with the input ends of two low-pass filters I, and the output ends of the two low-pass filters are respectively connected with the in-phase input end and the anti-phase input end of an add operation circuit; the output end of the add operation circuit is connected with the input end of a low-pass filter II; the output end of the low-pass filter II is connected with the input end of a voltage follower; and the output of the voltage follower is an expected signal. The generating circuit provided by the utility model has the advantages that a) the cost is low, the achievement of the generating circuit only requires an isolator and a piece of integrated operationally amplifying chip; and b) the generating circuit is provided with a symmetrical structure, can adapt to environmental changes to work accurately, is wide in use range, and has a high application value.