The invention relates to a high-fidelity fixed-depth water sample collection device, which includes a frame body, which is used to set up at the wellhead of a monitoring well; a lifting device, which is installed on the frame body; a sampling cylinder, which includes a cylinder body and a sampling bottle And the cover assembly, the sampling bottle is installed in the cylinder, which is filled with anti-oxidant gas, the side wall of the cylinder has a water inlet connected to the inside, the cover assembly is arranged in the cylinder, and the lifting device is connected with the cylinder for driving The cylinder body moves up and down; the uncapping mechanism is installed on the frame body and is connected with the cover assembly, which is used to drive the cover assembly to move to open or seal the water inlet and the mouth of the sampling bottle; the temperature detection device, the temperature The detection device is installed in the cylinder. Advantages: The structural design is reasonable, the sampling water does not come into contact with the air during the whole sampling process, which ensures the high fidelity of the water sample, makes the detection result true and reliable, and the temperature is measured in situ, which greatly reduces the measurement error.