The voltage measuring devices running in a converter station can lack the means to detect an effective transient characteristic. To improve the security of a UHVDC transmission project, this paper researches a field test technology of transient step response suitable for a DC voltage measurement device. It analyses the generation mechanism of step overshoot voltage and response delay in DC voltage measurement, and proposes a field test method of transient step response based on a low voltage subsection test. It uses AC and DC voltage superposition to realize the test for transient step overshoot voltage, realizes the step response delay test through a transient step test, generalized polynomial curve fitting and cubic spline interpolation. It builds a system to test the device on site, and the results show that the test technology can meet the needs of the field detection for transient step response. This work is supported by the National Natural Science Foundation of China (No. 51707090) and the Science and Technology Project of State Grid Corporation of China “Key Technologies Research and Application of On-site Test and Operation and Maintenance Optimization of UHVDC Control and Protection System” (No. 5210EF180013).