In the rice planting area of Northeast China, the large amount of rice straw with low moisture content was tough to crush, and the poor quality of straw crushing and scattering would seriously affect the quality of subsequent soil preparation. In order to meet the demand of soil preparation for straw returning and reduce the number of machine tools under the ground operation, the connection device which could combine the straw crushing returning and soil preparation were designed. According to the characteristics of the duplex operation machine, the interaction and matching between straw crushing and ploughing were considered in the design process. The connection device were analyzed theoretically from three motion planes: horizontal vertical surface, longitudinal vertical surface and level surface, and the reliability of the connection device were analyzed by simulation. Through theoretical analysis, the width matching of horizontal vertical surface, the position matching of longitudinal vertical surface and the dynamics matching of level surface were studied. According to the connection parameters obtained from theoretical analysis, the structure of the connection device was designed. The static analysis and dynamic analysis of the key connecting device were carried out by ANSYS Workbench, and the device were designed to meet the requirements of strength and reliability in the transportation state. The field experiments of duplex operation and section operation showed that the duplex operation machine could achieve the working stability of the plough. The experiments showed that the average ploughing depth was 17.3cm, the stability of ploughing depth was 91.2%, the average ploughing width was 119.2cm, and the stability of ploughing width was 93.6%. The vegetation coverage rate of duplex operation was 95.7%, and that of section operation was 98.3%, which was no significant difference between them. Moreover, the fuel consumption of duplex operation was less than that of section operation, and the fuel consumption could be saved by 3.15kg/hm2. The research result can provide reference for the development and interactivity design of connection device of duplex operation machine.