The invention provides a high phosphorus high calcium liquid compound fertilizer, including the following raw materials by weight: 0.2-1.2 parts of disodium octoborate tetrahydrate, 0.05-2 parts of EDTA (ethylene diamine tetraacetic acid)-Mn, 0.05-1.8 parts of EDTA-Zn, 10-50 parts of calcium fertilizer, 0.5-6 parts of magnesium fertilizer, 20-75 parts of phosphoric acid, 1-9 parts of urea phosphate, 2-13 parts of ammonium polyphosphate, 3-15 parts of potassium fertilizer, 0.5-4 parts of a cosolvent, 0.5-4.5 parts of a stabilizer and 8-40 parts of water. The invention also provides a preparation method and a use the method of the high phosphorus high calcium liquid compound fertilizer. The high phosphorus high calcium liquid compound fertilizer enables phosphate radicals and calcium ions to stably coexist in the liquid phase to avoid production of calcium phosphate and other insoluble precipitates, effectively improves the utilization rate of phosphorus and calcium liquid fertilizers, is good in fluidity, high-enriched in nutrients, and suitable for automatic fertilizing operation of large area, can significantly improve the fertilizing efficiency, and has the advantages of being time saving, labor saving, fertilizer saving, fast in fertilizer efficiency and the like.