For the fortuitous failure period of I/O card, its life obey exponential distribution,the failure rate that is mainly affected by the temperature is a constant.With the temperature as the covariable,a failure rate model was proposed based on proportional hazard model in this paper.Based on the research and development of DCS system reliability monitoring system,statistical analysis to obtain the failure rate of the I/O card at different temperatures.The M-estimation in robust regression is used to estimate the parameters of the model and the failure rate is analyzed qualitatively and the failure rate is corrected.The example analysis shows that the model have the ability to represent the actual failure rate,which can provide evidence for fault diagnosis of DCS,life management and preventive maintenance.