The utility model relates to railroad locomotive brake valve maintaining technologies and specifically discloses a brake valve main valve preliminary check testing stand. The utility model aims to solve the problem that currently there is no available equipment used specially for brake valve preliminary check tests. The brake valve main valve preliminary check testing stand comprises an air source, an air storage reservoir, a train pipe air reservoir, an accelerating alleviation air reservoir, an auxiliary reservoir, a brake air reservoir, a local reduction air reservoir, a bidirectional air reservoir, a train pipe, an accelerating alleviation pipe, an auxiliary pipe, a brake pipe, a local reduction pipe, a leakage detecting pipe, a flow meter, a differential pressure meter, a first double-needle pressure gauge, a second double-needle pressure gauge, a third double-needle pressure gauge, a single-needle pressure gauge, an air filter, a first lubricating oil atomizer, a second lubricating oil atomizer, a first pressure-regulating valve and a third pressure-regulating valve. The brake valve main valve preliminary check testing stand is suitably used for maintaining 120/120-1 type brake valves.