Abstract: Non-contact electrostatic voltmeters, also known as explosion-proof electrostatic voltmeters, are important instruments for preventing electrostatic hazards. The accuracy and reliability of their measurements are of great importance. However, the current automatic calibration process suffers from significant measurement uncertainties. In accordance with the JJG 192—2019 "Verification Regulation for Non-contact Electrostatic Voltmeter," this paper analyzes the causes of uncertainty in the automatic calibration process of non-contact electrostatic voltmeters. Based on this analysis, an improved automatic calibration equipment for remote programmable calibration of non-contact electrostatic voltmeters has been developed. The equipment includes remote programmable distance adjustment and zero out, electromagnetic interference shielding, and automatic grounding equipment, which ensure complete isolation between the operator and the high-voltage sources. The actual measurement results show that the improved equipment reduces the systematic measurement uncertainty of 10% to 50% of the traditional method to 0.3%, meeting the calibration requirements of non-contact electrostatic voltmeters.