The invention provides an energy recovery system for a hydraulic system, which comprises a hydraulic test unit and an energy recovery unit, wherein the hydraulic test unit comprises a power supply device, a hydraulic pump, a controller, a test stand and an oil distributor; the energy recovery unit comprises a motor switch, a hydraulic motor, a power generator, an electric energy distributor, a storage battery, a first electric quantity detection device and a second electric quantity detection device. The hydraulic motor is used for converting pressure energy of the hydraulic system into kinetic energy; the power generator is used for converting the kinetic energy of the hydraulic motor into electric energy; the electric energy distributor preferentially charges the power supply device with the electric energy; and when the power supply device is fully charged, the electric energy distributor charges the storage battery. According to the system, on the basis that the original hydraulic test unit is not changed, the energy recovery unit is added to substitute the test stand as a preheating load unit in a preheating process before the hydraulic system is used; the unloaded energy of the test stand is converted into the electric energy; and the electric energy is stored for testing laboratory emergency equipment or illumination.