The invention relates to a test apparatus of a microcomputer bus protection apparatus, and specifically relates to a portable microcomputer bus protection apparatus tester. The tester comprises a housing, and a power switch, a bus branch display panel, a reset button and an indication lamp group which are arranged on a front panel of the housing, wherein the bus branch display panel is provided with a bus wiring diagram, and a branch knife position indication lamp, a branch knife position knob switch and a bus tie breaker position knob switch are installed on the bus wiring diagram in an embedded mode; and the housing is internally provided with a circuit board, the circuit board is composed of an input loop and an outlet loop, and the input loop comprises a knife position input branch, a bus tie input branch and a failure input branch. The application is convenient, the functions are complete, when a bus protection test is carried out, input and outlet motion conditions are obviously seen, and the test efficiency of bus protection can be greatly improved.