Linear active disturbance rejection control(LADRC), which is independent of the mathematical model of the controlled object, has great application prospect in the industrial process, and the parameters tuning of LADRC is an important part of its application in the industrial process. In view of the fact that the PID controller is mostly used in industrial control, through the analysis of the structure of second-order LADRC and the transfer function of its state observer, it can be concluded that there is a strong relationship between the second-order LADRC and the PID controller, and the LADRC has better control performance than PID. This paper presents a method to get the initial value of LADRC parameters directly from the existing PID parameters to achieve better control performance and based on the first-order inertia plus time-delay model, the PID tuning methods are transformed into the second-order LADRC parameterS tuning methods. Finally, the simulation of the benchmark system verifies the effectiveness of the proposed method.