The invention discloses a multi-working-condition direct-current cable water circulation forced cooling test platform under a direct-current heat source and relates to the field of direct-current cable conveying capability improvement and test. A submarine cable login section area is complex in condition and great in influence on environment and weather, different laying working conditions need tobe simulated on a bottleneck section area to study the influence of environmental factors on the conveying capability, and corresponding measures are provided to improve the conveying capability. Theplatform comprises an environment area module, a direct-current application unit, a water circulation cooling unit, a cable temperature measurement unit and an environment information acquisition unit, two cables which are laid in the environment area in parallel are short-circuited at the tail end through a short-circuit terminal to form a closed through-current loop, the direct-current application unit, the water circulation cooling unit and the cable temperature measurement unit are all connected to a PLC control cabinet, and the PLC control cabinet and the environment information acquisition unit are connected to a computer overall control system. According to the platform, the direct-current conveying capacity of the cable under different laying working conditions can be really reflected; and the promotion effect of water circulation forced cooling on the conveying capacity is verified through a long-time continuous test.