Abstract: In response to the engineering problem of critical degradation of insulation electrical strength and voltage tolerance of medium voltage variable speed electric drive systems caused by high-altitude and low-pressure environments, this paper conducts research on insulation design correction methods for medium voltage variable speed electric drive systems. Adopting a step-by-step strategy, the altitude correction factor is first deconstructed and coupled based on the altitude gradient and pressure parameters, in order to achieve accurate calibration of the insulation design correction coefficient; Based on this coefficient, gradient reconstruction and quantitative correction of key insulation gaps within the system are carried out to calculate the minimum safe distance under high-altitude conditions; By using the method of reverse mapping and reverse tracing of tolerance threshold, the rated impulse withstand voltage and insulation coordination level of the overall system are verified based on the corrected gap value. Comparative experiments show that this method can effectively suppress corona discharge and nonlinear growth of dielectric loss in low-pressure environments, significantly improving the insulation reliability and operational robustness of the system under altitude gradient changes.