The invention provides a lithium tetrafluoro oxalate-phosphate preparation method which is simple and practical and can be applied to large-scale industrial production. The lithium tetrafluoro oxalate-phosphate preparation method provided by the invention is characterized by comprising the specific steps: firstly, weighing lithium oxalate, putting weighed lithium oxalate into a 316L stainless-steel reactor A with a jacket and a filtrating device, and thoroughly stirring weighed lithium oxalate for 2-6 hours, so as to fully dissolve weighed lithium oxalate into anhydrous HF; and then, adding phosphorus pentachloride and hydrogen fluoride into another 316L stainless-steel reactor B with a jacket and a filtrating device, and carrying out reaction. The lithium tetrafluoro oxalate-phosphate preparation method has the advantages that lithium tetrafluoro oxalate-phosphate is prepared from low-cost raw materials, the preparation method is simple, the disadvantages of other methods that the number of reaction steps is large, the consumption of reaction is high and impurities in the final product are too many are overcome, and thus the cost can be greatly reduced.