Abstract: In this paper, the test and research on the effect law of onion drying properties were carried out by using a self transform vacuum and far infrared device under the conditions of 3～7mm for thickness of the sliced onion, 40～70 ℃ and -0.04～0.08MPa for vacuum desiccator. The drying mechanism and the effect of different factors on vacuum far infrared drying process were investigated. Regression index equations were established on the basis of the three factor quadratic rotation regressive test and the better parameter range was obained.