Based on the example about the data communication of HNC and PLC, a communication scheme between HNC and PLC was proposed based on ProfibusDP. The system was made of upper level industrial control computer PLC S7300 and hydraulic controller HNC100. In this technique, SIEMENS S7300 PLC was a master station and communicated with slave station HNC100 by ProfibusDP, so the realtime data communication of the local data was realized.