The invention relates to a method for recycling battery-grade iron phosphate in a lithium iron phosphate battery and preparing a lithium iron phosphate positive material by utilizing a waste lithium ion phosphate battery, and relates to a method for recycling a battery and preparing the battery positive material by utilizing the waste battery recycled material, solving the problems of the traditional method for recycling the LiFePO4 lithium ion battery positive electrode that the purity of the obtained element or substances is low and the obtained element or substances cannot be used for preparing the LiFePO4 lithium ion battery positive electrode. The method comprises the steps: I, crushing a positive pole piece, and carrying out heat treatment; II, dissolving the crushed positive pole piece in an acid solution; III, charging a surface active agent; IV, charging an alkaline solution, thereby obtaining a battery-grade iron phosphate; V, charging sodium carbonate to obtain a lithium carbonate; VI, mixing iron phosphate, lithium carbonate and a carbon source reduction agent; and VII, calcining. In the process for recycling the battery-grade iron phosphate in the lithium iron phosphate battery and preparing the lithium iron phosphate positive material by utilizing the waste lithium iron phosphate battery, no secondary pollution is produced, and the comprehensive and high-added-value recycling of the waste lithium iron phosphate battery can be realized.