Abstract: The paper briefly introduces the constitution and operation of a computer-based monitoring and controlling system for aquatic products breeding. This system is a typical computer-based distributed control system that is composed of industrial control computer as upper level computer and single-chip microcomputer control system as lower level computer. On the basis of the fault tree analysis, the essential idea for raising operation reliability of the system was produced to assure security and reliability of system and build up practicability of the system. The essential idea was using software and hardware redundant resources of single-chip microcomputer and industrial control computer to constitute error tolerating system, reforming the topology of fault tree to reduce the number of low-order minim cut sets, so as to lower the probability of the top event. By evaluating fault tree, the essential measures were also introduced mainly as follows: reducing the man-made operating misplay; making reliability design of single-chip microcomputer system and improving error correction program and fault diagnosis program in control software of single-chip microcomputer control system and industrial control computer. Theoretical analysis and experimental results indicate that ways presented in this paper can effectively remove negative effects induced by part of hardware faults, software defaults, man-made misplay and outer electromagnetic disturbance, etc, in this system, so as to ensure the performance of aquatic products breeding.