Whole plastic mulching and furrow planting has been widely adopted as a drought resistant cultivation model in the northwest arid area of China in recent years. For further integration agronomic requirement of cultivation pattern of double width filming and covering soil on double ridges and improving the level of mechanization construction performance and efficiency of seedbed, a combined operation machine for double width filming and covering soil on double ridges was designed, which synchronously realized institutional operation once such as rotary tillage, ridging, fertilization, double width filming and covering soil and suppressing on double ridges. Based on the transmission route of combined operation machine, the key parts were designed and selected, and the operation parameters and power dissipation of rotary blades, fertilizing device and soil elevating-seedbed covering mechanism were determined. The operation process of scraper type soil lifting device and horizontal two-way spiral soil conveyer were analyzed, and the necessary work conditions to make sure that the covering soil on the all parts of double width filming seedbed were analyzed and calculated. The discrete element method was applied to simulate the device with soil elevating-seedbed covering mechanism dynamic operation process of soil elevating, transporting and covering. The characteristics of soil transporting and covering in each working link were analyzed, the related factors that affected the effect of covering soil were discussed. The field experimental results showed that under the condition of operation speed of 1.10m/s, the mechanical damage degree of day lighting surface of plastic film was 39.8mm/m2, the qualified rates of soil width covered on seedbed film edge was 94.5%, the qualified rates of soil width covered on center of large ridge was 91.6%, the qualified rates of soil depth covered on seedbed was 97.5% and the qualified rates of ridging height was 93.2%, which were up to the relevant work quality evaluation specification requirements, and the experimental results met the design requirements of combined operation machine. The field test conditions was consistent with the simulation result. The research results would provide an important reference for researching and developing the supporting agricultural machinery equipment which constructed seedbed of whole plastic-film mulching on double ridges in northwest arid area of China.