Provided is a nuclear fuel assembly positioning system having a built-in solenoid valve box in an apparatus for testing nuclear fuel used in an atomic power plant. A work table is installed at a predetermined position within an underwater fuel storage pool, and a solenoid valve box connected to two pneumatic hoses extending from the outside is integrally installed on an test table so as to drive the test table, so that only the two pneumatic hoses simplified as a gas supply hose and a gas discharge hose are connected with the test table, and thus the nuclear fuel assembly is accurately and rapidly positioned as to be able to conveniently perform testing without the structures around the hoses being interfered with when pneumatic motors are operated.