The invention discloses a tungsten-titanium alloy nanocrystalline floating grid structure used for a flash memory, pertaining to the technical field of micro-electronics. The structure comprises a silicon substrate as well as a silicon oxide layer, a high k (dielectric constant) thin film, a tungsten-titanium alloy nanocrystalline charge storage layer, a barrier layer and a grid material layer which are covered on the silicon oxide layer successively. The structure improves memory properties of a non-volatile memory unit of the floating grid structure, such as programming/erasing efficiency, programming/erasing (P/E) speed, effective charge memory power, data maintenance property and programming/erasing tolerance. The invention also discloses a method for manufacturing the tungsten-titanium alloy nanocrystalline floating grid structure. The method is simple and convenient and is compatible with the traditional CMOS silicon planar technology.