The new developments in the photoinitiated cross-linking mechanism of polyethylene and significant breakthrough of its industrial application are reviewed. The enhanced photoinitiation system, the dynamics of photoinitiated crosslinking, the optimum conditions, the crosslink microstructures, the crystal morphological structures and related properties, and the photo- and thermo-oxidation stability of photocrosslinked polyethylene (XLPE) materials have been studied systematically. A new technique of photocrosslinked insulated XLPE wire and cable is described in detail. It can be expected that the future applications of photoinitiated crosslinking technique of polyolefins are very promising.