The invention discloses an open caisson W-shaped excavation sinking construction method. The open caisson W-shaped excavation sinking construction method includes the construction steps that S1, an open caisson is arranged above a to-be-constructed region; S2, multiple bays of the open caisson are divided into an excavation region, a reserved region and an auxiliary region through calculation; S3,firstly, soil is taken from the excavation region, the open caisson sinks overall, while the open caisson sinks overall, the soil is taken from the reserved region and the auxiliary region, and it isguaranteed that a certain height difference exists between soil mass in the excavation region and soil mass in the other two regions; S4, when the open caisson sinks to a designed jointing position,the top of the open caisson is jointed, and after jointing is completed, the numbers of the bays of all the regions are adjusted through calculation; and S5, S3 and S4 are repeated until the open caisson sinks to a designed elevation position, wherein in S3, if the soil is taken from the excavation region, the open caisson does not sink, and the auxiliary region is excavated until the open caissonsinks overall. The open caisson W-shaped excavation sinking construction method has the beneficial effects of being easy to construct and high in safety, and can be widely applied to the technical field of bridge middle-large-size open caisson sinking construction.