The invention relates to an analog quantity control method for a feed pump set with different powers, in particular to an analog quantity control method for a set with two 50 percent steam feed pumps and a 30 percent electric feed pump. Boiler water level PID control over automatic non-disturbance non-balance switching of any pump is achieved, boiler water level full automatic control is achieved, the efficiency of a unit is improved, and unit safety is guaranteed; the three pumps are controlled by one PID regulator, a function F(X1) is formed by the power pressure curves of the pumps to correct powers of different pumps to be matched, the inverse function F(X2) of the F(X1) is equal to F-1(X1) and is adopted as an electric pump track value to achieve non-disturbance non-balance switching of running of different pump sets, the maximum value among the electric pump track value and the output of the two steam feed pumps is taken, therefore, the variable proportional adjustment with two pumps in PIC automatic control at the same time and one pump in PID control can be achieved, and any one or two of the three pumps can be grouped to be in PID automatic control to run.