Abstract: A theoretical model of high power and high efficiency picosecond laser oscillator pumped by 888nm LD was fabricated. Based on simulation calculation, resonance theory, ABCD law, self-consistent condition and continuous passive mode locking condition, absorption property of crystal Nd:YVO4 at 888nm wavelength, appropriate element parameters and mode parameters, and mode locking parameters were analyzed and calculated. Parameters of a model of picosecond laser oscillator were obtained based on the above calculated results. The results indicate that 61.5W high average power can be generated with 120W pump power and optical to optical conversion efficiency is 51.3％. The model helps for experiment on picosecond laser oscillator with high average power.