The invention provides a method for improving communication message usage rate in a PROFINET protocol. The method for improving the communication message usage rate in the PROFINET protocol includes following steps: dividing a communication time segment into a plurality of data time segments; dividing a standard data frame into a plurality of data domains, and assigning the data domains to a field slave station device; achieving different demands of high speed data transmission of the field slave station device according to the divided data time segments and the divided data domains. The method for improving the communication message usage rate in the PROFINET protocol achieves the divided data time segments in an improved communication protocol, can increase the number of slave stations connected with a main station on the premise of improving data transmission rate, and furthermore increases the amount of effective load data, decreases the number of cycle periods of the data, and improves the data transmission rate by using the improved PROFINET protocol.