The invention relates to a method for preparing high-density lithium ferric phosphate, which comprises the following steps of: adding a lithium salt, a ferric salt, a phosphorus-containing compound and doping metal-containing elements into a dispersing agent by the conventional method, and performing ball mill twice; performing drying and predecomposition for 3 to 10 hours; crushing, adding at least one of lithium dihydrogen phosphate or potassium dihydrogen phosphate as a bonding agent in an amount which is 1 to 5 percent based on the weight of a predecomposition product, performing ball mill for 1 to 5 hours, and processing according to the prior art to obtain the high-density lithium ferric phosphate. In the method, the ball mill is performed twice in the first step, so that granules are fine; the grain size can be controlled within the range of between 300 and 2,000 nanometers, so that raw materials are mixed uniformly; more importantly, due to the addition of the bonding agent, the bonding among the granules is enhanced, the stacking density of products is improved, and contact conductivity among the granules is reduced; and the prepared products have good crystallization, simple structure and uniform grain fineness distribution and do not contain impure phases, the tap density is between 1.4 and 1.8 g/cm<3>, the specific surface area is between 5 and 11m<2>/g, the compaction density of pole pieces is between 2.4 and 2.8 g/cm<3>, and the specific capacity of first discharging at the room temperature is between 140 and 160 mAh/g.