Messages communication delay is composed of transmission delay and handling delay. According to IEC 61850 standard， the generic object-oriented substation event（GOOSE） message is mapped onto the data link layer direct， which can decrease the transmission delay. The message handling delay in an intelligent electronic device（IED） of substation is discussed， and a hard real-time operation system in IED is adopted owing to the shortcomings of the traditional foreground/background system in handling real-time messages. According to the environment of mixed message transmission of real-time message and non-real-time message， a method is designed to guarantee disposing GOOSE message in real-time on a real-time application interface（RTAI） operating system. The experiment results demonstrate that this method is valid and practicable. The research result is significant for the design of IED process layer communication with IEC 61850.