Aiming at solving the problems, such as inadaptation to baled straw, insufficient loading capacity, and easily blocked soil covering device, that happened in the first generation orchard straw mulching machine, a self-unbaling orchard straw mulching machine was developed. The machine consisted of tracked chassis, unbaling-spreading device, bin and soil covering device, etc. The unbalingspreading device was a toothed belt structure and installed at the rear of the bin. To adapt to a variety of straw bales and improve bale breaking ability and mulch uniformity, after analyzing the process of unbaling and spreading, the key parameters such as inclination angle, height and rotating speed of the device were determined. To reduce drag during rope cutting and bale breaking, a triangular knife-tooth was designed, and the distribution of the knife-teeth was planned based on the analysis of straw compression and disturbance area. A double-sided opposite-throwing soil covering device was designed to cover soil on the surface of straw layer synchronously. The test results showed that the straw loading capacity was increased to 3.1 times of the original machine. When the speed of the straw mulching machine was 0.8~1.4 km/h and the rotating speed of the unbaling-spreading device was 180~240 r/min, the thickness of the straw mulching layer was 5.1~18.1 cm with standard deviation not more than 3.4cm, and the thickness of the soil covering layer was 2.3~4.0 cm with no interruption happened during soil-covering, meeting the requirements for straw mulching in orchard. The established straw mulch thickness model, with a determination coefficient of 0.9672, can be used to guide the parameters adjustment in actual production. The machine realized the operation integration of straw unbaling, inter-row mulching and thin soil covering, which laid foundation for improvement of orchard straw mulching mechanization technology and equipment performance.