Abstract: As a key electronic product of space aircraft, flight control computer participates in the flight control of aircraft throughout the process, which has the characteristics of strong real-time performance, high reliability, radiation resistance and long life. A variable redundancy architecture four-redundancy computer technology is proposed, which combines the self-detection (BIT) technology and on-duty voting technology. It can realize different redundancy architecture management through fault detection, self-recovery, on-duty control, multi-mode voting and other technologies. Combined with the engineering practice, two four-redundancy architecture modes are analyzed from the system architecture of the flight control computer. Through the self-detection technology, the fault detection and location can be carried out quickly, and then the promotion and degradation management and reconstruction of the four-redundancy can be realized by the on-duty voting, and the reliability model can be established for the analysis. The reliability of four-mode parallel mode in 5 years (about 45, 000 hours) is as high as 0.995. The technology has been successfully applied to a space shuttle.