The invention provides a combustion device for researching soot characteristics in a low-pressure environment. The combustion device comprises a stainless steel low-pressure sealed cabin, a diffusion flame combustor, a gas mass flow control device, a high-voltage arc ignition device, an observation window, an auxiliary cleaning device, a digital display programmable logic controller (PLC), a vacuum pump group, an operating pressure stabilization device, a balance pressure air source and a detachable calibration tool clamping groove. The vacuum pump air exhaust and the balance pressure air source are simultaneously controlled through the control device in a low-pressure environment in the cabin, so that target pressure of the cabin is achieved. The inflow of two paths of gases of the combustor and the balance pressure air source is controlled by the gas flow controller, and after a pipeline is connected each time, the gas tightness at each joint of gas transport pipelines in the whole system is checked. A pressure meter is designed on a quick release upper flange plate. Operating pressure can be set and is dynamically monitored in real time through a PLC control interface, and the inflow of fuel gas, following wake air and the balance air source can be set.