Abstract: The development and the application of China’s first nuclear safety level digital I&C system FirmSys platform in the main control station (MCS） are conducted. PowerPC series high-performance processor is used on the hardware of the main controller unit. Non-commercial operating system, task scheduling without interruption and static fixed memory distribution design are used on the embedded software. Communication between two control stations uses the one-way transmission mode. MCS meets the design requirements of fail-safe in the event of a failure and loss of electric power. MCS software has passed the verification and validation (V&V) of the independent third party from German ISTec Organization. All the cards in MCS have passed the environmental, electromagnetic compatibility and seismic tests required by relevant standards, and have been successfully applied in ACPR1000 Nuclear Power Plant and HTR Nuclear Power Plants.