The invention discloses a stand-by power source detection method of a wind power generation set variable pitch system. The method comprises steps that: a variable pitch system storage battery set is connected with a PLC (Programmable Logic Controller) in the variable pitch system, the PLC is connected with a host computer; performance parameters of the variable pitch system storage battery set are firstly detected by the host computer, whether the performance parameters of the storage battery set can satisfy use requirements are determined according to a storage battery voltage drop and capacity relation report form, and a single battery having a fault is identified according to a determination result and is changed. The stand-by power source detection method is advantaged in that performance of the storage batteries is determined before hoisting of a blower fan, so timely change is carried out to prevent the storage batteries from being changed soon after hoisting, and power generation capacity loss and manpower cost increase caused by shutdown because of change of the storage batteries are avoided.