The invention discloses cesium and rubidium brazing flux containing zinc tetrafluoroborate hydrate. The cesium and rubidium brazing flux comprises, by mass percentage, 0.001%-0.01% of rubidium fluoride, 10.0%-50.0% of cesium fluoride, 0.01%-5.0% of aluminum oxide, 0.01%-5.0% of potassium fluoride, 0.001%-0.25% of zinc tetrafluoroborate hydrate and the balance aluminum fluoride. According to the cesium and rubidium brazing flux containing zinc tetrafluoroborate hydrate, zinc tetrafluoroborate hydrate is added, the usage amount of rubidium fluoride is reduced greatly, brazing of the same material of aluminum-aluminum, dissimilar materials of aluminum-cooper, dissimilar materials of aluminum-steel and an alloy material of aluminum-aluminum can be achieved, the material cost is reduced remarkably, and the brazing flux has excellent capacity of removing FeO, Fe2O3, NiO, Cr2O3 and other oxide on the surface of aluminum alloy or steel; and the brazing flux on the base metal has excellent wetting performance, spreading performance and penetrating performance, the brazing seam strength can reach 125 MPa to 145 MPa, and the requirements for low lost, high reliability and environmental-friendly manufacturing of the industries of air conditioners, refrigerator complete machines, refrigeration accessories, rail transit and energy can be met.