The invention discloses a commissioning method and system of a cold standby converter transformer in an extremely cold environment. The commissioning method includes: checking the work state of each operation device in a converter station; determining whether an operation condition of the cold standby converter transformer is satisfied according to the work state of the operation device; if yes, conducting a no-load charging switch-on test on the cold standby converter transformer, determining a switch-on control method, and adjusting the operation devices; and if not, adjusting the work stateof each operation device in the converter station. The temperature distribution of the cold standby converter transformer in the extremely cold environment is determined through statistics and simulation experiments, corresponding preheating processing is performed according to the temperature distribution, and the damage to the cold standby converter transformer due to starting of the cold standby converter transformer in the extremely cold condition is avoided; and the cold standby converter transformer is put into operation, and correct commissioning of the cold standby converter transformer is ensured.