With the continuous advancement of the ‘carbon peak, carbon neutralization’ construction project, the low carbon station area power supply system has become an important part of the new power system. Firstly, the dynamic mechanical model of plant load change in typical low-carbon industrial parks is established by using the centralized humidifier of the park as the flexible load, and it is verified that the first-order system can better describe the dynamic process. Secondly, the auto-regressive model with additional input is used for system identification, and the first-order model is obtained by order reduction. Thirdly, the transfer function of the model system is reduced to a differential equation by using the inverse Laplace transform, and the analytical solution of the differential equation is obtained. The pre-start time is determined according to the expected humidity and the target time. Finally, for the case beyond the range of application, the model parameters can be re-identified. The results show that this method can accurately and conveniently determine the adaptive pre-start time of air humidification equipment, and has a wide range of application scope, which is an efficient method. The application of this method is not limited to air humidification equipment, and can be used for public load in low-carbon station areas.