The invention provides a cable trench and a water inflow preventing method for the cable trench. The cable trench comprises a trench body and cover plates. The cable trench is characterized in that the left side and the right side of the trench body are respectively provided with at least one rail groove, the bottom face of each cover plate is provided with two sets of idler wheels, wherein one set of idler wheels run in the rail grooves in the left side of the trench body, the other set of idler wheels run in the rail grooves in the right side of the trench body, and an installing shaft of each idler wheel is installed on a shaft base; all the shaft bases are fixedly installed on the bottom faces of the cover plates; a connecting part is arranged on the butt joint working face of each cover plate; in every two adjacent cover plates, a sealing strip made of rubber is arranged on the butt joint working face of the connecting part at the front end of one cover plate, and the other cover plate is provided with a sealing groove corresponding to the sealing strip; each sealing strip is curved, and the middle of each sealing strip is higher than the two ends of the corresponding sealing strip; a water guide groove is formed in the upper surface of each sealing strip; the left end and the right end of the cross section of each sealing strip are formed in a symmetric trapezoid mode; the cross section of each corresponding sealing groove is also in a trapezoid shape; exhaust elbows are arranged on the cover plates; handles are arranged on the cover plates. The cover plates can be conveniently adjusted, and water is prevented from flowing into the cable trench.