The invention relates to a regeneration method of a styrene extraction lean solvent. The method includes: adding desalted water and raffinate oil into part of a to-be-regenerated extraction lean solvent in a styrene extraction device to conduct extraction treatment so as to gather polymer impurities of the extraction lean solvent in the raffinate oil and dissolve the extraction lean solvent, the degradation product of the extraction lean solvent and a small amount of solvent within the raffinate oil in water, thus forming a polymer-raffinate oil phase and an extraction lean solvent-water phase, and then carrying out pressure reduced distillation to remove water from the extraction lean solvent-water phase so as to realize regeneration recycling of the styrene extraction lean solvent; and incorporating the polymer-containing raffinate oil into a heavy fraction line of the device to realize comprehensive utilization. The method provided by the invention can make the quality of the circulating extraction lean solvent in the styrene extraction device always at a good level and the pH value stable, at the same time can reduce the solvent content of the raffinate oil, improves the extraction efficiency of styrene, reduces solvent loss and waste residue discharge, and is in favor of long-period stable operation of the device.