In order to study the integration technology of field bus and industrial Ethernet, a scheme of gateway between PROFINET IO and PROFIBUS PA is proposed. Employing Siemens EB200 IO Evaluation Board to access PROFINET IO network, the gateway is implemented with a PROFIBUS PA as an external connection driver. Correlated software packages are designed to realize the mutual mapping of data models and network functions between the two protocols. The function test and performance test prove the feasibility of the gateway. It also shows good compatibility with GSD engineering systems.