The invention discloses a reconstruction and expansion expressway side slope anti-seismic ecological protection system and a construction method thereof. A multistage side slope is designed, a criss-cross drainage system is arranged on the side slope, and an anchoring system of a specific structure is driven into a rock stratum in a cross X shape and movably connected with a hanging net comprising two stages of grids; the construction method is simple and easy to apply; and the technical problems that the reconstruction and expansion expressway side slope anti-seismic ecological protection system is not long in protection time and inconvenient to maintain are solved. A good fixing effect is achieved on the expressway side slope; water and soil loss is prevented; the side slope environment is beautified; and meanwhile, the maintenance cost is low, and the protection time is long.