Effects on volatile and semi-volatile organic components (VOCs) in water have been studied by comparison of three sampling methods, which were applied in typical groundwater contaminated site. The results show that DS technique of sampling is stable and reliable, better than both bailer sampler and peristaltic pump in terms of collecting water samples to obtain content of VOCs in water. Factors Factors with impact on loss of VOCs during sampling are negative pressure, contact with outside atmosphere and turbulent flow in order from strong to weak, where loss of VOCs caused by negative pressure is apparently higher than that caused by contact with outside atmosphere and turbulent flow; comparative analysis indicates that short-time sampling with sampler made of stainless steel, polyfluortetraethylene, and silica gel tube has no strong corrosion over water sample, and the effect on samples are negligible through analysis of chemical constituents. Based on that, DS sampling method is designed, applicable to sampling of underground water of open well, 110cm monitoring well, and shallow layer- 30cm shallower and 60cm shallower, and in the meanwhile, with introduction of automatic control circuit and sensors for water level, pressure, temperature, PH value and EC, the function of measuring and storing in-situ physical and chemical parameters accompanying sampling is achieved.