The invention relates to a testing cable sealing device for a container for simulating a deepwater environment explosion test. According to the technical scheme, two to fifteen cable holes (8) are formed around the center of a flange cover plate (1) and located in a protection cover (2); each cable hole (8) is a through hole which is formed by three sections, the hole diameter of the upper portion is larger than the hole diameter of the lower portion, a sprue (7), sealant (6) and a ring washer (5) are concentrically arranged on the middle section of each cable hole (8) from bottom to top, each compression bolt (4) is fixedly connected with the upper section of the corresponding cable hole (8) through threads, and the lower end of each compression bolt (4) is tightly pressed on the upper plane of the corresponding ring washer (5); a testing cable (3) sequentially penetrates through the protection cover (2), the corresponding compression bolt (4), the corresponding ring washer (5), the corresponding sealant (6) and the lower section of the corresponding cable hole (8) to be connected with an underwater impact wave pressure sensor. The testing cable sealing device is high in compression resistance, good in sealing performance, easy to assemble, wide in application range, and capable of meeting the requirement for simulating the 0.01-Kg TNT equivalent explosion test at the 200 m underwater environment.