Abstract: A spiral magnetic fluid composite sealing structure of a roller bit comprising a cone leg and a roller, wherein the roller and the cone leg are in rotatable connection in a fitting manner through a roller inner hole and a cone leg shaft journal, a sealing groove is formed in an opening end of the roller inner hole, and a spiral magnetic fluid sealing assembly is arranged in the sealing groove. Through the arrangement of the spiral magnetic fluid sealing assembly, a spiral sand discharging effect is realized, compared with a passive sealing mode, the sealing performance is greatly improved by active sand discharging mode, and the service life of sealing is significantly prolonged; a slurry sealing effect of magnetic fluid seals is realized, resulting the sealing gap is tightly sealed under the magnetic action; in addition, the automatic compensation function of magnetic fluid can also be realized.