The invention discloses a method for obtaining a primary heavy current under a low practical load. The method comprises the following steps of S1, taking any phase in three-phase lines of a high voltage system as an input line, and setting a test line on the input line, wherein the test line comprises a current booster and a to-be-tested electrical equipment which are connected in series; S2, setting a primary side of the current booster on the input line, and carrying out series connection on a secondary side of the current booster and the to-be-tested electrical equipment; and S3, carrying out connection on an end of the to-be-tested electrical equipment away from the current booster and the input circuit. The invention also discloses a system for obtaining the primary heavy current under the low practical load. According to the method and the system, a heavy current is realized through utilization of a current booster and a high voltage is realized in a mode of realizing direct connection with the input circuit, so under the condition that an input line load is relatively low, the to-be-tested electrical equipment is enabled to be located in a heavy current and high voltage to-be-tested environment, and investment cost and test cost are effectively reduced.