A polyphosphate and a low-temperature preparing method thereof

A polyphosphate and a low-temperature preparing method thereof are disclosed. The method includes (1) a step of preparing slurry, namely a step of reacting nitric acid and phosphate rock according to a mass ratio of (1.1-1.3):1 to obtain the slurry, (2) a step of neutralization and evaporation, namely a step of subjecting the slurry and ammonia gas in a mass ratio of 15-25:1 to a neutralization reaction, adding auxiliaries after the neutralization, adding into an evaporator, and reacting under atmospheric pressure at a temperature lower than 170 DEG C to obtain a material liquid, (3) a step of mixing, namely a step of mixing the material liquid with one or more selected from a group consisting of a nitrogenous fertilizer, a phosphorus fertilizer, a potassic fertilizer, an auxiliary material and trace elements to obtain a mixture, and (4) a step of granulation, namely a step of directly granulating after the material liquid in the step (2) is evaporated until the water content is less than 1.2%, or granulating