The development of low-cost concentrators is one of the important ways to reduce the cost of solar thermal utilization on a large scale. In order to reduce the material cost, a new design idea of water-injected Fresnel condenser is proposed. The water-injected Fresnel condenser adopts a hollow triangular prism composed of thin flat glass, and the use of lens materials is reduced by injecting pure water into the hollow part, thereby reducing the cost. The design theory of the concentrator is studied and the corresponding optical model is established. Monte Carlo ray tracing method is used to study the optical performance of the concentrator under different sun incident angles, and compared with the traditional Fresnel concentrator. Build a test prototype and conduct a preliminary light gathering experiment. The research results show that, compared with the traditional Fresnel concentrator, although the water-injected Fresnel concentrator has a certain loss of concentrating effect, the average loss of concentrating efficiency is 5.40%, but the experimental prototype has obvious concentrating effect, the light spot width is also in good agreement with the theoretical situation, and it is feasible for engineering applications.