The invention provides an apparatus and a method for directly producing low-carbon olefins by using coal as a raw material through syngas. The apparatus comprises a coal gasification unit, a syngas purification unit, a reaction-to-olefin unit, and a gas recovery and olefin separation unit, wherein a syngas mixer is arranged between the syngas purification unit and the reaction-to-olefin unit. According to the present invention, the unconverted syngas with high hydrogen-to-carbon ratio is completely recovered, and is mixed with the purified syngas with low hydrogen-to-carbon ratio, the water-gas shift process with characteristics of high energy consumption and high water consumption can be eliminated; the reaction-to-olefin unit uses the oxide and molecular sieve compounded bifunctional catalyst, such that the selectivity of the low-carbon olefin in the product distribution can be greatly increased; and compared to the methanol-to-olefin process through conversion of syngas, the processof the invention has advantages of water consumption reducing, energy consumption reducing, investment reducing, unit olefin cost reducing and internal return rate improving.