Disclosed is a method for continuously preparing mixed hydroxide precipitate from a laterite nickel ore by hydrometallurgy. Primary-precipitated mixed hydroxide precipitate particles are used as crystal nuclei, by controlling precipitation process conditions, the quantity of the crystal nuclei, and reaction time of the crystal nuclei, primary mixed hydroxide precipitate crystal nuclei gradually grow, and crystal forms become larger. By controlling the number of cycles, a proportion of returned seed crystals, and a homogenization ratio with precipitants, mixed hydroxide precipitate particles with narrow particle size distribution, dense particles, and better sedimentation effect are obtained, thereby reducing a moisture content of mixed hydroxide precipitate. The preparation method in this disclosure plays a certain guiding role in practical production and has good application prospects.