The invention relates to a method and device for overpressure bypass test of flexible and direct converter valves, and the method comprises the following steps of firstly determining sub-modules to betested in a first valve assembly and a second valve assembly; charging a first auxiliary valve, a second auxiliary valve, a first test valve and a second test valve by using a charging branch; performing boost bypass operation on the sub-modules to be tested in the test valve by controlling the two test valves and the two auxiliary valves to trigger the over-voltage protection logic of the sub-modules after the voltage of the sub-modules to be tested rises to an over-voltage protection setting value, and controlling the sub-modules to be tested at the bypass to make the voltage of the sub-modules to be tested gradually decrease; and when the system current rapidly increases, triggering the over-current protection logic, and controlling all sub-modules to be blocked to make the current gradually decrease. The method is used to detect the stress characteristics of key components of the sub-modules under fault overvoltage and over-current and the correctness of the sub-module protectionlogic.