In this study, with the aim of achieving a high-efficient, low-noise and light-weight radiator cooling fan, the authors have conducted the visualization experiment and the CFD analysis of air flows around fans, and finally developed a new propeller fan whose blades are connected together by a ring formed inward from their tips. Owing to this ring, the fluid noise due to vortices caused by blade tip etc. was reduced by approximately 2dB. In addition, the fan efficiency was improved by around 5 points by modifying the shape of the ring so as to facilitate smooth air flow to it. Since the strength of the blades was reinforced by connecting them with the ring, the blade thickness was decreased and, as a result, the fan weight was reduced by 20g.