Crosslinked polymer electrolyte (CPE) and composite polymer electrolyte are two of the most promising polymer electrolyte (PE) systems for improving the resistance to Li dendrite growth, but the trade-off and agglomerated effects of these PEs hinder the development of safe Li metal battery (LMB). Herein, a new class of crosslinked composite polymer electrolyte (CCPE) with the combination of confined ionic liquid (IL) polymer network and homogeneously dispersed boron nitride nanosheet (BNNS) for LMB is reported. This UV-curable CCPE is formed on electrode via in-situ crosslinking of a precursor solution in a rapid and solvent-free step, and the assembly process of LMBs and interfacial contact/adhesion are maximum optimized. The critical point of this CCPE is that a facile channel for Li+ transfer and a robust skeleton for confining IL and strengthening interface are simultaneously achieved via the introduction of network structure and 2D BNNS in PE. Consequently, the LiFePO4ǀLi batteries involving CCPE show a great improvement in the charge-discharge cycling stability and rate performance compared with those of the cells with pure CPE. This study offers an effective and facile strategy for fabricating dendrite-resistant CCPE with potential applicability in next-generation energy storage systems.