A method for synthesizing nano-lithium iron phosphate without water of crystallization in aqueous phase at normal pressure, characterized by comprising the steps of: a. preparing lithium phosphate: phosphoric acid is added in an aqueous solution of a lithium salt having a lithium content of 0.2-4 mol/L and heated to 30-80°C, with the molar amount of phosphoric acid added being 1/3 of that of lithium in the solution, and then adjusted to a pH of 9-11 by adding an aqueous sodium hydroxide solution while stirring, and further subjected to solid-liquid separation and washing, giving lithium phosphate as solid; b. preparing an aqueous phase suspension of lithium phosphate: the resulting lithium phosphate is dispersed in water into a suspension of lithium phosphate having a lithium phosphate concentration of 0.1-1 mol/L; c. preparing a ferrous salt solution: a ferrous salt is dissolved into water to prepare a ferrous salt solution having an iron content of 0.5-3 mol/L, and adjusted to a pH of 1-3 with an acid; d. preparing nano-lithium iron phosphate without water of crystallization: the suspension of lithium phosphate prepared in b is placed in a reactor and heated to boiling at normal pressure while stirring, vaporized steam is cooled and refluxed and under reflux, the ferrous salt solution prepared in c is slowly added, with the molar amount of the ferrous salt added being 0.97-1.0 time of that of lithium phosphate in the reactor and the addition time being controlled to be within 1-3 h, and after the addition, the reaction is continued under reflux with stirring for 2-8 h and then subjected to solid-liquid separation, washing and drying, giving nano-lithium iron phosphate without water of crystallization as solid and a corresponding mother solution of lithium iron phosphate; e. recovering and recycling lithium in a mother solution of lithium iron phosphate: the remaining mother solution of lithium iron phosphate after separating nano-lithium iron phosphate without water of crystallization as solid prepared in the previous step is transferred into a reactor, phosphoric acid is added while stirring, with the molar amount of phosphoric acid added being 1/3 of that of lithium in the mother solution, and then heated to 30-80°C, and adjusted to a pH of 9-11 by adding a sodium hydroxide solution, and further subjected to solid-liquid separation and washing, giving lithium phosphate, which is recycled back to the step b. a. preparing lithium phosphate: phosphoric acid is added in an aqueous solution of a lithium salt having a lithium content of 0.2-4 mol/L and heated to 30-80°C, with the molar amount of phosphoric acid added being 1/3 of that of lithium in the solution, and then adjusted to a pH of 9-11 by adding an aqueous sodium hydroxide solution while stirring, and further subjected to solid-liquid separation and washing, giving lithium phosphate as solid; b. preparing an aqueous phase suspension of lithium phosphate: the resulting lithium phosphate is dispersed in water into a suspension of lithium phosphate having a lithium phosphate concentration of 0.1-1 mol/L; c. preparing a ferrous salt solution: a ferrous salt is dissolved into water to prepare a ferrous salt solution having an iron content of 0.5-3 mol/L, and adjusted to a pH of 1-3 with an acid; d. preparing nano-lithium iron phosphate without water of crystallization: the suspension of lithium phosphate prepared in b is placed in a reactor and heated to boiling at normal pressure while stirring, vaporized steam is cooled and refluxed and under reflux, the ferrous salt solution prepared in c is slowly added, with the molar amount of the ferrous salt added being 0.97-1.0 time of that of lithium phosphate in the reactor and the addition time being controlled to be within 1-3 h, and after the addition, the reaction is continued under reflux with stirring for 2-8 h and then subjected to solid-liquid separation, washing and drying, giving nano-lithium iron phosphate without water of crystallization as solid and a corresponding mother solution of lithium iron phosphate; e. recovering and recycling lithium in a mother solution of lithium iron phosphate: the remaining mother solution of lithium iron phosphate after separating nano-lithium iron phosphate without water of crystallization as solid prepared in the previous step is transferred into a reactor, phosphoric acid is added while stirring, with the molar amount of phosphoric acid added being 1/3 of that of lithium in the mother solution, and then heated to 30-80°C, and adjusted to a pH of 9-11 by adding a sodium hydroxide solution, and further subjected to solid-liquid separation and washing, giving lithium phosphate, which is recycled back to the step b.