The invention relates to the field of coal gasification technology, especially to a slag removal system and a method thereof. According to the invention, distribution of flow field around a slag removal pipe can be improved, instability and obstruction of slag removal due to uneven distribution of flow field are avoided, and potential safety hazards such as abrasion of a central jet pipe, etc. canbe avoided. The slag removal system comprises a gasifier, the bottom of which is provided with a gas distribution plate. A gas distribution plate zone is above the gas distribution plate. The bottomof the gas distribution plate extends downward to provide with a slag removal pipe, which penetrates through the bottom of the gasifier. A columnar slag removal channel which is communicated with thegas distribution plate zone is formed at the bottom of the gasifier and is communicated with a slag hopper system through a connection pipe nipple. One end of the connection pipe nipple, close to theslag removal pipe, is provided with an annular gas distributor, which is used for distributing gas to the gas distribution plate zone through the columnar slag removal channel. A swirl flow field is formed in the gas distribution plate zone, and ash and slag fall down under the action of the swirl flow field and are discharged through the slag hopper system.