The invention relates to a lithium ion battery positive material, in particular to a preparation method for a lithium ion fast conductor modified lithium phosphate material. The preparation method is characterized by comprising the following steps: (1) according to the components of the lithium ion fast conductor, covering raw materials including a lithium source, an A source, a B source, an N source, a silicon source and a phosphorus source are mixed with lithium iron phosphate to be covered to form a precursor, and then the precursor is dried; (2) the obtained precursor is sintered in an inert atmosphere, the sintering temperature is 400-1,000 DEG C, and the soaking time is 2-20 hrs. In the preparation method, a layer of lithium ion fast conductor film is compound on the surface of a nano lithium iron phosphate, so as to greatly improve the power performance of the nano lithium iron phosphate; particularly, the glass state lithium ion fast conductor is a well-know favorable and stable lithium conductor, at the same time, favorable conductivity is acquired by adulterating a transition metal; and adopting the material prepared by the invention to manufacture batteries, more than 40 c high current charging / discharging can be achieved.