The invention provides a pneumatic unbalance detection method and device for a wind wheel of a wind generating set. The method comprises the steps that in the first set time period, the torque valuesof blade variable-pitch drive motors are collected one time every set time interval, and the variance of the torque values of the blade variable-pitch drive motors in the first set time period is figured out; whether blades are stressed abnormally or not is judged according to the torque values of the blade variable-pitch drive motors in the first set time periods within the second set time period, wherein the second set time period comprises a set number of continuous first set time periods; and when the blades are stressed abnormally, whether stress on the wind wheel of a draught fan is unbalanced or not is judged according to the maximum value and minimum value of the average value of the torque values of the blade variable-pitch drive motors as well as the average value. By means of the technical scheme, whether the torques of the blade variable-pitch drive motors are not balanced or not is judged without acquiring a large quantity of data, an algorithm is simple, and pneumatic unbalance caused by checking deviation of the mounting angle can be detected.