[en] The magnetron is a microwave source. The electron efficiency of the magnetron, which defines the efficiency of converting electron flux energy into energy of high-frequency fluctuations, is very high (up to 80%). Still, almost all of the remaining part is released as heat per anode unit, which leads to its heating. This temperature increase reduces the device useful life and causes magnetron failure. One way to remove the heat generated by the magnetron is to cool it, which, depending on the type and output of the magnetron, may be cooled by air or water. Therefore, In this paper, a water-cooling system for a 1kW magnetron with a frequency of 2.45 GHz is designed and simulated by using Comsol software (version 5.6) to study the temperature changes and distributes in the magnetron under the influence of water cooling and to compare it with the state where there is no cooling. The simulation results showed that in the absence of cooling, over time (10 minutes), the magnetron temperature reaches 5680℃, which causes the magnetron to melt. With the cooling design, we observed that the magnetron does not change temperature after 10 minutes of continuous operation in the water-cooling system and has temperature stability. This result allows the magnetron to be used for more extended periods in industrial and consumer applications such as microwave ovens.