The invention relates to a horizontal shaft tidal current energy water turbine with snail spiral blades. The horizontal shaft tidal current energy water turbine comprises a main shaft, a machine case, a thrust bearing, a coupler, a power generator, a rack, a base and a water guide taper; and the lower portion of the machine case is supported by the rack and the base. The horizontal shaft tidal current energy water turbine is characterized by further comprising the snail spiral blades in two-dimensional snail spiral line shapes, a similar-taper hub soaked into water tide and a sealing cover; the power generator is connected with the similar-taper hub through the coupler and the main shaft, the sealing cover is arranged at the connecting position of the main shaft and the similar-taper hub, and the water guide taper is arranged at the position, on the back side of the similar-taper hub, of the tail of the machine case; and the snail spiral blades are evenly distributed on the periphery of the similar-taper hub to rotate at a constant speed in a manner that the snail spiral blades conducts gradual change stretching in the axial direction of the similar-taper hub through the thrust bearing to form spatial warping shapes. According to the horizontal shaft tidal current energy water turbine, hydraulic power friction collision is greatly reduced, and the inlet water head losses are reduced, so that the energy obtaining efficacy of the water turbine is accordingly improved, and the aim of smooth passing of ocean fish schools is achieved.