The direct-ignition technology of an entrained-flow coal-water slurry gasifier with hot-oxygen burner (HOB) is presented. Experimental tests were carried out using diesel oil and coal-water slurry in a bench-scale entrained-flow opposed multi-burner (OMB) gasifier. Using a CCD camera equipped with high-temperature endoscope, flame images inside the gasifier were recorded and subsequently processed. The results show that the HOB diesel flame is more stable than the normal two-channel burner flame typically used. Entrained-flow coal-water slurry gasifiers can start up using the HOB directly without a higher preheated wall temperature. An HOB can potentially save gasifier preheating time and operation costs and enables a wide range of future applications.