In the Large High Altitude Air Shower Observatory project, Muon detectors will be built at 4400m above sea level. As water cerenkov detector, 44 tons of ultrapure water should be infused into the Muon detector. In this cold area, once the water inside the Muon detector freezes, consequence would be very serious. In this paper, a simulation of water temperature is built, the simulation data are consistent with the temperature data of Muon detector at yangbajing Tibet. Using the same simulation with air temperature, soil moisture and temperature of Dao cheng, an antifreeze solution was designed. Through two years of testing, the design is successful.