A power-split hydro-mechanical hybrid transmission system with an automatic adjustment function includes an input member, a hydraulic transmission mechanism, a split mechanism, a convergence mechanism, an output member, a clutch assembly, and a brake assembly. The clutch assembly connects the input member to an input end of the split mechanism, connects an output end of the split mechanism to an input end of the hydraulic transmission mechanism and an input end of the convergence mechanism, and connects an output end of the hydraulic transmission mechanism to the output member. An output end of the convergence mechanism is connected to the output member. The clutch assembly and the brake assembly provide a continuous transmission ratio between the input member and the output member. The power-split hydro-mechanical hybrid transmission system enables multi-mode continuously variable transmission and has energy reuse and emergency support functions.