The invention discloses a hydro-electric mixed driving system used for engineering machinery, which comprises a pilot control valve, a main valve, a motive power device and a controller. The invention is characterized in that the motive power device is a mixed motive power device, and consists of a hydraulic motor, a motor generator and a speed reducing machine through coaxial connection, an electromagnetic overflow valve is respectively connected in parallel on the high-pressure oil output end of the hydraulic motor, the controller controls the motor generator, the electricity generation output of the motor generator is connected with an energy accumulator, the output end of the energy accumulator is connected with the electric input end of the motor generator, an electromagnetic valve block is arranged between the pilot control valve and the main valve, a pressure sensor is respectively arranged on the input and output end of the electromagnetic valve block and on a high-pressure oil inlet opening of the hydraulic motor, and each pressure signal is respectively input into the controller. The hydraulic motor and the motor generator of the invention are in coaxial connection, the braking overflow energy is recovered to be used as electric energy of the electric motor, the hydro-electric mixed driving on the engineering machinery is realized, the energy consumption of the wholemachine is lowered, and the use cost is saved.