ＲＷ２２型空调软卧车的空气调节系统原是固定逻辑式接触器继电器控制系统，该系统可靠性差，占的空间体积大，易损坏，常因故障而停机，因此，不能满足人们对软卧车舒适性的要求，为提高软卧车空调系统的可靠性，减少故障率，采用可编程序控制器代替原控制系统中的继电器部分。文章分析了原系统控制要求，论述了用ＰＣ实现的控制过程及电气控制保护 RW22 air-conditioned soft sleeper air conditioning system was originally a fixed logic contactor relay control system, the reliability of the system, accounting for large space, easy to damage, often downtime due to failure, therefore, can not meet people on the soft car comfort Requirements, in order to improve the soft sleeper air conditioning system reliability and reduce the failure rate, the use of programmable logic controller instead of the original control system in the relay section. The article analyzes the original system control requirements, discusses the use of PC to achieve the control process and electrical control protection