The invention discloses a reliability detecting system and method of a direct current transmission current changing variable network side sleeve. The system comprises a nitrogen fulfilling device, a test instrument, a communication device and a controller; the controller sends a test item command to the nitrogen fulfilling device or the test instrument by the communication device and receives the test data of the test on the current changing variable network side sleeve 1 performed by the nitrogen fulfilling device and the test instrument, to judge the reliability of the current changing variable network side sleeve. The invention discloses a reliability detecting method for detecting various performances of the current changing variable network side sleeve by the nitrogen fulfilling device and the test instrument formed by a 1.2/50mu s lightning surge voltage generator, a 250/2500mu s standard operating impulse generator, a long-term power frequency withstand voltage testing device, a 60s power frequency withstand voltage and margin withstand voltage testing device, a dielectric loss factor tan sigma and a capacitance testing instrument, an insulation oil performance testing instrument and a temperature-rising testing instrument. The reliability detecting system and method of the direct current transmission current changing variable network side sleeve are capable of improving the replacing feasibility test of the current changing variable network side sleeve.