Low-permeability/tight sandstone reservoirs generally have a high starting pressure gradient，which will have a certain influence on the CO2 flooding development scheme design. The commonly used methods for testing the starting pressure gradient have the limitations of inaccurate test results or long test time. In order to improve the experimental efficiency and test accuracy，an experimental method for testing the water-phase starting pressure gradient of low-permeability/tight sandstone reservoirs was proposed. By the method for observing the timing of droplet emergence in the early stage and establishing a multi-stage stable displacement in the later stage，the minimum starting pressure gradient and the pseudo starting pressure gradient were measured simultaneously in a displacement experiment. This method has the advantages of a short test period，easy observation of experimental phenomena，and high test accuracy. The method was applied to test the core samples from an actual oilfield，and the test results of the minimum starting pressure，the minimum starting pressure gradient，and the pseudo starting pressure gradient were obtained. A prediction model for the minimum starting pressure gradient of the water phase was also established for the target area.