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Up-conversion photoluminescence (UCPL) referrs to the elementary process where low-energy photons are converted into high-energy ones via consecutive interactions inside a medium.When additional energy is provided by internal thermal energy in the form of lattice vibrations (phonons),the processis called phonon-assisted UCPL.Here,we report the exceptionally large phonon-assisted energy gain of up to ～ 8kBT (kB is Boltzmann constant,T is temperature) on all-inorganic lead halide perovskite semiconductor colloidal nanocrystals that goes beyond the maximum capability of only harvesting optical phonon modes.By systematic optical study in combination with a statistical probability model,we explained the nontrivial phonon-assisted UCPL process in perovskites nanocrystals,where in addition to the strong electron-phonon (light-matter) coupling,other nonlinear processes such as phonon-phonon (matter-rnatter) interaction also effectively boost the up-conversion efficiency.