Provided are an ultra-high molecular weight, ultra-fine particle size polyethylene, a preparation method therefor and a use thereof. The viscosity average molecular weight (Mv) of the polyethylene is greater than 1 ?10, and the polyethylene is spherical or sphere-like particles having a mean particle size of 10-100 祄, a standard deviation of 2-15 祄 and a bulk density of 0.1-0.3 g/mL. Using the polyethylene as a basic polyethylene, a grafted polyethylene can be obtained by means of a solid-phase grafting method; and a glass fiber-reinforced polyethylene composition comprising the polyethylene and glass fibers, and a sheet or pipe prepared therefrom; a solubilized ultra-high molecular weight, ultra-fine particle size polyethylene; and a fiber and a film prepared from the solubilized ultra-high molecular weight, ultra-fine particle size polyethylene may also be obtained. The method has simple steps, is easy to control, has a relatively low cost and a high repeatability, and can realize industrialisation. The polyethylene of the present invention has both an ultra-high molecular weight range and an ultra-fine particle size range, and is particularly suitable for processing applications, greatly expanding the application field and the applicable range of an ultra-high molecular.