The utility model relates to the field of launch canister water pressure testing, in particular to a launch canister water pressure testing tool which comprises a supporting base. The sealing plate set is composed of two clamping plates, and the two clamping plates are installed at the two ends of the supporting base respectively and can get close to each other or get away from each other; the twoends of the opposite-pull connecting rod are arranged on the two clamping plates in a penetrating mode respectively, and the length of the section located between the two clamping plates can be adjusted; aiming at the problems in the prior art, the utility model aims to provide the launch canister water pressure test tool which only provides a function of clamping and sealing two ends in a waterpressure test for an aircraft launch canister and saves the water pressure test cost.