A system for testing the safety of electricity includes steps as following. First step is inserting a testing apparatus into a socket of utility power. Second step is providing a first amplifier and rectifier unit for measuring a first voltage wave as no-loading. Third step is providing a signal capturing unit at driver circuit for capturing an instant load cycle current wave. Fourth step is providing a second amplifier and rectifier unit for simulating a second voltage wave according to the instant cycle current wave. At least, a processing unit provides for comparing the first voltage wave with the second voltage wave. Therefore, the above-mentioned method is provided for determining the quality of household electricity wire and further improving the electricity safety.