The measured results of E-601B water surface evaporator is easily influenced by manual operation and meteorological condition， so this paper introduced development of a non-overflow-hole evaporator of water automatic replenishing based on the traditional E-601B water surface evaporator. Based on the principle of Mariotte bottle， the device removed the overflow -hole of traditional E-601B water surface evaporator， added Mariotte bottle， reading device and Balance bottle， so as to realize evaporator’ s water automatic replenishing effect and improve the observation accuracy during rain duration. The synchronous observation analysis was made in 2015. The results show that the correlation coefficient R2 between the evaporations from the two evaporators reached 0.9998， which means application of non -overflow -hole evaporator of water automatic replenishing can make evaporation measurement more convenient， and improve the measurement accuracy.