The invention discloses an automatic load change control method used for an air separation plant. The automatic load change control method comprises following steps that firstly, PFD data of key process parameters under various stations of flow design of the air separation plant are obtained; secondly, the variable serving as the final product flow is determined and serves as the target value set in the load change process of a flow operator; thirdly, the key middle variable is determined and is used for calculating the set point of a final PID controller; fourthly, the PID controller participating in the automatic load change is determined; fifthly, through fitting, a fitting function between the parameters in the second step and the third step, with the variable in the third step as the dependent variable and the variable in the second step as the independent variable is obtained; sixthly, through fitting, a fitting function between the parameters in the third step and the fourth step, with the variable in the fourth step as the dependent variable and the variable in the third step as the independent variable is obtained; seventhly, according to work point data of one process parameter under different stations, through the polynomial function, all work point models are subject to interpolation, and the load change liner change track of the process parameter is obtained; eighthly, starting and stopping of the automatic load change need to meet a certain condition; ninthly, according to the difference of the flow, the above parameters can be increased or decreased.