Abstract: Degassing efficency is an important aspect which affects the calibration of water radon meter, the accuracy and repeatability of measured radon value of water sample.The observers and researchers on radon in groundwater hue paid a great attention to this.In this paper, a compnehensire experimental study has been made for multi-factor effects ondegassing efficency such as one time and twice degassing, vaeuum degree, humidity, speed, time, mode, valume of water sample, the valuta and shape of diffusion bottle.And quantitative effective results and control methods have been presented.