The present invention relates to an electroplating preparation method for a carbon nano-tube/cobalt-phosphorus composite coating with characteristics of high hardness, corrosion resistance, wear resistance and low friction coefficient. According to the electroplating preparation method, a platinum net is adopted as an anode, a work-piece requiring plating is adopted as a cathode, a mixed solution containing 20-60 g/l of a cobalt salt, 2-10 g/l of carbon nano-tubes, 30-70 g/L of sodium dihydrogen phosphate, 50-100 g/l of a sodium salt, 10-30 g/l of boric acid, 1-4 g/l of saccharin, 0.01-0.2 g/l of a surfactant, 10-100 g/l of a complexing agent, and the balance of distilled water is adopted as an electroplating solution, electroplating is performed after the electroplating solution is subjected to an ultrasonic vibration treatment, and the carbon nano-tubes are further subjected to a sensitization activation treatment. The prepared carbon nano-tube/cobalt-phosphorus composite coating has characteristics of high hardness, excellent wear resistance, low friction coefficient, excellent corrosion resistance and simple preparation method, and is widely used in the fields of automotives, machinery, precision manufacturing and aerospace.