The invention discloses a spraygun of a gasification chamber for desulfurizing granular magnesium. The spraygun comprises a metal gun core the lower end of which is provided with the gasification chamber; the outer circumferential surface and the underside of the gastification chamber are covered with a refractory working liner respectively; the inner surface of the sidewall of the gasification chamber is an outer convex arched surface; the lower end of the gasification chamber is provided with hemline skirt; a plurality of zigzag protrusions with downward tooth tips are arranged on the innersurface of the hemline skirt along the circumferential direction or a plurality of metal short columns are welded on the inner surface of the hemline skirt; and the inside of the refractory working liner is distributed with a plurality of solid riveting pieces. The structure of the gasification chamber avoids the promoting action of the prior conical top corner to slag adhesion, reduces the slag adhering speed and the slag cleaning frequency and delays the deforming speed of a metal member of the gasification chamber; and the irregular hemline skirt can absorb the whole deformation of the hemline of the sidewall of the gasification chamber, strength the comprehensive strength and non-deformability of the wall of the gasification chamber and finally achieve the aims of prolonging the service life of the spraygun, reducing the manufacturing cost for the spraygun and improving the use performance of the spraygun.