The present invention described a test method for unit re-modification, in which there is a test end and a host end. The method generated a sample pattern at a test end, generates a control pattern and modifies a re-modification unit. Otherwise, an experimental pattern is generated and then whether or not the original function is retained after modifying the re-modification unit is determined according to the result of comparison of the control pattern and experimental pattern thereon. The present invention is used to test the internal function module of specific software or hardware, and ensure that the proper function is retained after re-modification.