It is suitable for the sampling of liquid medium. The needle assembly is continuously purged. During the sampling process, the needle assembly and sampling can be continuously purged by inert gas. The medium is purged through the coupling valve first, and then the medium in the sample chamber is purged by the inert gas. Sweep into the sampling bottle, the coupling valve has the function of quantification and simultaneous control of multiple valves, making the sampling process more accurate and safer for the operator, and the process pressure is separated from the sampling pressure. The system can be used for higher pressure sampling processes. condition