A optimum reliability distribution method of precise conveying robot system based on precision and cost controls was proposed. The method sets up a reasonable and effective system reliability optimum distribution mathematic model using network system optimum principle to adjust the relation among system precision

reliability

and cost

and to meet the requirements of reliability and precision. The method also deploys the mixed successive coordinating method to solve proposed mathematical model. The research results achieve the optimum reliability distribution of the robot system and show that the method can be used in reference on setting up optimum reliability distribution of 6 or more dimensions for a precise conveying robot system or more-complicated large systems.