Abstract: Problems like non-linearity，time delays and uncertainties still exist in the pH value control of sodium hydrosulfite synthesis process.The parameter self-adjustment can not be realized by conventional PID control plus artificial control.Thus，the desired effect on pH value control can hardly be achieved.To solve these problems，a fuzzy adaptive PID control method is proposed in this paper.The synthesis principle and reaction equation of sodium hydrosulfite are introduced.The pH value control based on acid-base neutralization is analyzed and the transfer function of the system is confirmed.The fuzzy adaptive PID controller is designed.The simulational analysis is made by using Matlab／Simulink and empirical experiments are also conducted.Our results show the fuzzy adaptive PID control has such advantages as small overshoot，short adjustment time and strong anti-interference ability compared with the conventional PID control，and thus the pH value control is effectively achieved.