Abstract: Present studies usually optimize the design of solar heating station and the heating network respectively in the optimization design of centralized solar heating systems. In this study,a joint model to simultaneously optimize the equipment capacity and heating network pipe diameter of the centralized solar heating system,with the optimization objective of minimization of life cycle cost,is established and solved by genetic algorithm. The results are analyzed and compared with the conventional method and engineering method through an exemplified case,which show that 1)the joint optimization model could avoid the low solar fraction and high heating pipe resistance that do not meet the requirement;2)the optimal minimum water supply temperature decreases from 60 ℃ to 45 ℃ as the solar fraction increases from 50% to 100%;3)with the increase of solar fraction,the ratio of the water tank volume to solar collector area increases,while the pipe diameter of the heating network remains unchanged.