In China, especially in the northwest region, alfalfa is often planted in mountains and hills, which makes mechanized harvesting become a big problem. The small selfpropelled mower, which is flexible and easy to move, is regarded as a proper solution to the problem. Taking the adverse working condition and the harvest requirements of alfalfa into consideration, the profiling device is the key part of this kind of mower. The research theoretically analyzed the profiling device which consists of sliding palm, spring, linkages and elevating hydraulic cylinder. Building the virtual prototype and carrying out the orthogonal experiment by using the model, the best parameters of the device were as follows: the sliding palm length of 188mm, the cutter bar tilt angle of 4.06°, the ratio of spring pull force to cutting table gravity of 0.85, and the advance speed of 2m/s. By using the optimized mower conditioner test in the field, the result of test showed the validity of the simulation. Besides, under the same working condition, the height of stubble was 7% as low as which was cut by prototype without optimization, and what’s more, the optimized mower worked 75% as fast as the prior machine.