A synchronous sliding mechanism for a movement guide of a side door, comprising: a guide rail, a first connecting rod mechanism, and a second connecting rod mechanism, wherein: the first connecting rod mechanism comprises a fixed base, a first connecting rod and a second connecting rod; and two sliding ends on the guide rail are provided on other ends of the first connecting rod and the second connecting rod respectively, and when the guide rail reciprocates in a horizontal axial direction, the two sliding ends are close to or far away from each other; the second connecting rod mechanism comprises a third connecting rod and a fourth connecting rod, characterized in that ends of the first connecting rod and the second connecting rod on a same side are pivotally connected to the fixed base; the first connecting rod and the second connecting rod are located on two sides of a horizontal central axis of the fixed base; in that the second connecting rod mechanism comprises a sliding base, and in that the third connecting rod and the fourth connecting rod are symmetrically provided in the horizontal central axial direction of the fixed base; the sliding base and the fixed base are located on a same side of the guide rail; and ends of the third connecting rod and the fourth connecting rod on a same side are pivotally connected to the sliding base, and other ends are pivotally connected to the first connecting rod and the second connecting rod respectively; the synchronous sliding mechanism further comprising a horizontal shaft, wherein one end of the horizontal shaft is fixed on the fixed base and another end of the horizontal shaft is slidingly matched with the sliding base. the first connecting rod mechanism comprises a fixed base, a first connecting rod and a second connecting rod; and two sliding ends on the guide rail are provided on other ends of the first connecting rod and the second connecting rod respectively, and when the guide rail reciprocates in a horizontal axial direction, the two sliding ends are close to or far away from each other; the second connecting rod mechanism comprises a third connecting rod and a fourth connecting rod, characterized in that ends of the first connecting rod and the second connecting rod on a same side are pivotally connected to the fixed base; the first connecting rod and the second connecting rod are located on two sides of a horizontal central axis of the fixed base; in that the second connecting rod mechanism comprises a sliding base, and in that the third connecting rod and the fourth connecting rod are symmetrically provided in the horizontal central axial direction of the fixed base; the sliding base and the fixed base are located on a same side of the guide rail; and ends of the third connecting rod and the fourth connecting rod on a same side are pivotally connected to the sliding base, and other ends are pivotally connected to the first connecting rod and the second connecting rod respectively; the synchronous sliding mechanism further comprising a horizontal shaft, wherein one end of the horizontal shaft is fixed on the fixed base and another end of the horizontal shaft is slidingly matched with the sliding base.