The design method of real-time Ethernet EtherMAC master based on SMP architecture was proposed, while a field bus oriented motion control engine was developed, which was running in kernel space. To make the procedure of motion control program development easy, a cross-platform programming interface was created by making memory stack in a shared memory for transferring parameters. To reduce the coupling between the motion control engine and the field bus, and to enhance the adaptability of the engine to any other field bus, a bus abstraction layer was proposed and designed. The result from prototype shows that the motion control engine has a better ease of use and a better portability, and indirectly enhances the EtherMAC real-time performance.