Depth-fixed undisturbed water sample collection system and collection method for collecting undisturbed water sample at fixed depth in static water area

The invention relates to a depth-fixed undisturbed water sample collection system and a collection method for collecting an undisturbed water sample at a fixed depth in a static water area. The depth-fixed undisturbed water sample collection system comprises a sampling bottle, a sampler, an upper connection body and a graduated pipe, wherein the sampling bottle comprises a bottle body, a bottle cover, a pressing plate and a protection cap; the sampler comprises a water feeder, a hanging beam and a lower ring; the upper connection body comprises a lifting beam and an upper ring; the weight of the sampler is twice that of the upper connection body; the sum of the weights of the sampler and the upper connection body is more than 1.5 times the weight of water discharged by the sampling bottle, the sampler and the upper connection body below a water level. The depth-fixed undisturbed water sample collection system is mainly used for collecting a water sample containing volatile substances and oxygen-sensitive substances in a water well, a lake, a reservoir, an underground river and a slowly running river, so that high-fidelity water sample collection can be realized; furthermore, in hermitical storage and transportation processes, no redundant space exists in the sampling bottle, so that air oxidization is avoided.