The invention provides a method for obtaining the measurement of the optical remote-sensing load in-orbit MTF precision by employing a knife-edge method. According to the method, an MTF reference value is set based on a practically-tested MTF value, according to characteristics of the knife-edge method MTF test, key parameters are extracted based on knife-edge images obtained by the load during the practical test to generate a reference image, the reference image is calculated by employing the knife-edge method to obtain an MTF calculating value, the calculating value and the MTF reference value are compared, an absolute error and a relative error are obtained, and the MTF measuring precision (or the uncertainty) is obtained. The problem that according to the conventional precision analysis method, the optimal remote-sensing load in-orbit MTF measuring precision in practical measurement by employing the knife-edge method cannot be obtained or estimated is solved.