The tea garden soil is often compacted and contains stones and gravel. When applying fertilizer by trenching, problems such as insufficient trench depth and unstable fertilizer application depth may occur. Therefore, a tea garden soil loosening and trenching fertilizer application machine was created, based on the original reciprocating tea garden soil loosening machine, by matching the loosening mechanism with the fertilizer application mechanism to add the fertilizer application mechanism, so that the trenching and fertilizer application operation can be carried out in the loosened and crushed soil after loosening, and the fertilizer depth can be increased by using the soil thrown by the loosening mechanism. For the structural design of the fertilizer trenching and loosening device, the structural parameters were determined in accordance with the agronomic requirements of tea garden trenching and fertilizer application. A coupled simulation model of Recurdyn and EDEM was established, and through single-factor simulation, the type of trenching machine with the minimum trenching resistance was determined, and orthogonal experiments were conducted to optimize the structure and operation parameters, resulting in the optimal operation parameters combination of the entire machine: forward speed of 0.07m/s, entry angle of 20°, and blade angle of 77.7°. The field verification test results show that this machine has good fertilizer and trenching performance, and can complete the loosening, trenching and fertilizing operations in one go. The variation coefficient of fertilizer drainage depth stability is 93.6%, and the variation coefficient of fertilizer uniformity is 92.1%. It is close to the simulation results and meets the agronomic requirements of tea garden machinery.