The invention discloses a water stop plug special for a continuous two-channel underground water monitoring well pipe. The water stop plug is composed of an upper baffle, a lower baffle, a water stoprubber plug and a bolt. The upper baffle and the lower baffle are arranged at the upper end and the lower end of the water stop rubber plug respectively, the bolt penetrates through the upper baffle,the lower baffle and the water stop rubber plug, and the upper baffle, the lower baffle and the water stop rubber plug are arranged together. The water stop plug is safe and reliable in structure andconvenient to use, the rubber plug is mechanically pressed for water stop, the water stop effect is reliable, according to the water stop pressure withstanding requirement, the length of the water stop rubber plug can be customized, or water stop rubber plugs are connected in series, the water stop plug is specially used for continuous two-channel underground water monitoring well construction, and is a key part of a continuous two-channel monitoring well, building of the monitoring well cannot be completed if the water stop plug is lacked, target layer and non-target layer underground water is blocked in the pipe, the service life is long, environmental protection is achieved, and the underground water is not polluted.