The invention discloses an electrochemical method for testing intercrystalline corrosion of 316LN austenitic stainless steel and belongs to the technical field of corrosion. The electrochemical method comprises the following steps: firstly, performing solution treatment on a testing material at 1100 DEG C; then, making two test samples into electrochemical samples, grinding working surfaces, polishing the surfaces, and finally performing ultrasonic washing with deionized water; preparing a sulfuric acid solution, and adding potassium rhodanate and sodium chloride into the solution; putting the prepared solution into a constant-temperature water bath pot to keep the temperature; connecting an electrode, and soaking the samples into the solution for 10 minutes, thereby obtaining a stable open circuit potential; from the open circuit potential, scanning at a scanning speed of 40mV/minute until 300mV, and scanning back to the open circuit potential at the same scanning speed; recording the activation current Ia and the reactivation current Ir of the samples to be tested and test samples after the solution treatment; working out the difference between Ra values of the samples to be tested and the samples after the solution treatment, thereby obtaining intercrystalline corrosion sensitive value of the samples to be tested. By adopting the electrochemical method, the influence of uniform corrosion on the testing result can be eliminated, the testing result is 9-10 times greater than that of a standard DL-EPR method, and high reliability can be achieved.