A three-nucleus real-time improvement scheme based on the normal core+ RTLinux patch+ kernel preemption patches is proposed for its application in the fault recorder. The operation principle of three-nucleus Linux is described. The key technology of double buffer is designed to improve the real-time performance of recording data transmission. The testing software of Stress-Kernel RPM package and Amlat are used to test the new platform. The real-time maximum response of three-nucleus platform is 1.2 ms， while 99.999% of the interrupts are lower than 1 ms. Test results show that the three-nucleus Linux platform can satisfy the real-time processing requirement of the fault recorder.