The invention relates to an overhigh-power variable-frequency test device and a railcar for electric connection of a power source thereof. The railcar comprises an electric rail board and an electric car, wherein the electric rail board comprises a first overturning plate, multiple first wiring terminals and multiple rails arranged on the first overturning plate and multiple contact points distributed along the rails; the electric car comprises a second overturning plate, multiple rows of caster wheels and multiple second wiring terminals arranged on the second overturning plate; the first overturning plate and the second overturning plate are respectively connected with a mounting box of two parts which form a power source of the test device; the first wiring terminals and the second wiring terminals are respectively connected with wiring terminal rows of the two parts. When the railcar is in use, the caster wheels of the electric car are contacted with the contact points of the electric rail board in a one-to-one correspondence manner. Rapid wiring operation of tens of cable groups between high-voltage variable-frequency power source components on site can be realized only by virtue of overturning and locking, complicated and fussy labor for connecting cables is avoided, the working efficiency is obviously improved and misconnection or fumble phenomena are prevented.