A seedbed belt preparation device suitable for constructing rapeseed substrate block seedling transplanters was designed based on the large cavity of the boat type furrow opener and the characteristics of constructing a wide seedbed and a flat furrow bottom through the operation of the core ploughshare furrow opener， combined with the excessive connection of the similar ploughshare surface to solve the problems of poor stability of the furrow width， low flatness of the furrow bottom， and large soil disturbance， resulting in low seedling rate and high difficulty in soil covering operations in the operation of furrow opener device of rapeseed substrate block seedling transplanter. A mechanical model for the interaction between soil and preparation device was established. The main structural parameters for constructing a stable seedbed with a seedbed belt preparation device were determined. A four-factor and three-level quadratic orthogonal combination simulation test was conducted using EDEM and taking the operating speed， working depth， front-end width of the brush type surface，and edge angle of blade as factors， the soil disturbance amount and coefficient of variation of ditch width as evaluation indicators. The results of quadratic orthogonal combination test showed that the soil disturbance amount and the coefficient of variation of the ditch width was small when the working depth， the operating speed， the front-end width of the brush type surface and the edge angle of blade was 41 mm，0.52 m/s，40 mm，and 61°， respectively. The results of bench test under the optimal parameter combination showed that the soil disturbance amount was 13.01 cm² and the coefficient of variation of the ditch width was 8.52%. The results of field comparative test showed that the seedling bed equipped with the preparation device installed on the transplanting unit increased the seedling rate of the substrate block by 2.09 percentage points， decreased the coefficient of variation of the ditch width by 13.3%， reduced soil disturbance by 20.9%， and increased the compactness of the ditch bottom by 28.7% compared to the boat type opener， meeting the requirements for the construction of the rapeseed substrate block seedling transplanter.