The telemetric current fluctuation of infrared earth sensor motor for a certain type of satellite is discussed, which occurred in the satellite test. The brushless DC motor selected for the infrared earth sensor has the characteristics of low-speed and small-load. By analyzing the steady-speed driving circuit of this brushless DC motor, and according to the working principle of the circuit phase locking, the cause of the telemetric current fluctuation is demonstrated. The mechanism analysis shows that the telemetric current fluctuation of the brushless DC motor is caused by the current spike generated in the motor commutation being sampled by the sampling circuit, which neither affects the safe and reliable operation of the motor nor affects the product's service life on the ground and on-orbit. By optimizing the sampling signal generation software, the telemetric current fluctuation of the motor can be effectively avoided.