In this paper, a new technique are developed for optimal design of water distribution system besed on reliability. It applies a linear programming algorithm to the optimal design based on reliability. Within a small optimal search step range,the objective function and constraints can be expressed in the first order Taylor-expanding form,and three sub-models (a steady-state simulation model, a reliability model and a linear optimization model) are linked each in optimal searches. Thus, a traditional non linear problem can be solved by a linear model, the computing burden is significantly decreased. Therefore, the linear optimal model developed by the paper has more practical significance. In applies this paper, a new technique are developed for optimal design of water distribution system besed on reliability. It applies a linear programming algorithm to the optimal design based on reliability. Within a small optimal search step range, the objective function and constraints can be expressed in the first order Taylor-expanding form, and three sub-models (a steady-state simulation model, a reliability model and a linear optimization model) are linked each in optimal search. linear model, the computing burden is significantly decreased. the linear optimal model developed by the paper has more practical significance.