The invention discloses a method for controlling a pH value of stator cooling water. The method is used for controlling the pH value to an appointed interval and specifically comprises the following steps: firstly setting an interval required to be reached by the pH value, namely a pH lower limit value and a pH upper limit value, a step length and delay time of regulating valve corresponding to the pH lower limit value and the pH upper limit value, a pH limit exceeding value and delay time corresponding to the pH limit exceeding value according to a pH value control interval; controlling an electric regulating value according to upper and lower limits of the collected pH value, so as to enable the pH value to reach the interval; and switching on or off an electromagnetic valve of the system according to the pH limit exceeding value: when the pH value exceeds the pH limit exceeding value and a set time is up, switching off the electromagnetic valve, and when the pH value is smaller than pH limit exceeding value and a set time is up, switching on the electromagnetic valve so as to restore the normal operation of the system. By utilizing the method, the pH value can be conveniently controlled to reach a required interval without manual intervention.