Abstract: Acidbase neutralization is an important process in treatment of chemical industrial wastewater. The pH value control system introduced here adopted a parallel transforming approach with both PID control method and fuzzy control method. When the deviate of the system is low, PID control method is usually used for processing control. While the deviate of the system is high, computer fuzzy control method is usually used. The principles for designing of pH value computer fuzzy control system are described. The operation of fuzzy controller including fuzzy treatment,fuzzy regulating database setting,fuzzy calculating and counterfuzzy treatment are also introduced. To apply this control system in wastewater treatment processes could result in high treatment efficient and stable control of the treatment.