Abstract: Residues generated during the production of traditional Chinese medicine (TCM) are rich in organic matter and trace elements, serving as valuable biomass raw materials for organic fertilizer production with broad prospects for resource utilization. To achieve waste valorization and leverage the complementary decomposition characteristics of different organic materials, organic fertilizers were prepared using TCM residues. The residue was thoroughly mixed with cow manure at a 3∶10 wet weight ratio as the base composting material. Three commonly used additives — biochar (produced at different temperatures, and the addition amount is 7% dry weight), clay minerals (montmorillonite, and the addition amount is 7% dry weight), and a microbial inoculant (Aspergillus oryzae) — were incorporated. A 35-d aerobic composting experiment was conducted in a 50-L closed reactor to investigate the effects of different additives on nutrient transformation during the preparation of organic fertilizers, providing technical support for the production of efficient organic fertilizers. Nine treatments were established: no additive (CK); and adding biochar produced at 300 ℃ (300C), biochar produced at 500 ℃ (500C), biochar produced at 700 ℃ (700C), montmorillonite (M), A. oryzae (W), biochar produced at 500 ℃ + montmorillonite (500CM), biochar produced at 500 ℃ + A. oryzae (500CW), and biochar produced at 500 ℃ + montmorillonite + A. oryzae (500CMW). The results demonstrated that the addition of biochar, montmorillonite, and A. oryzae, either individually or in combination, increased the pile temperature and accelerated the composting process. Compared to the CK treatment, the treatments of 300C, 500C, 700C, M, 500CM, and 500CMW increased the humus content and reduced carbon and nitrogen losses. Specifically, the carbon losses were reduced by 19.52%, 20.07%, 18.55%, 7.06%, 27.12%, and 9.45%, respectively. N losses were reduced by 61.75%, 50.79%, 39.22%, 35.16%, 63.18%, and 20.33%, respectively. Among these, the W treatment yielded the highest increase in humus content, 27.00% higher than that of the control (CK). Biochar, montmorillonite, and A. oryzae promoted the maturation and humification of compost. Biochar addition enhanced the organic matter content of the fertilizer. Combined addition of biochar with montmorillonite was particularly effective in reducing carbon and nitrogen losses, and synergistic effects were observed. Conversely, the addition of A. oryzae was more effective at accelerating the humification of organic materials. Thus, biochar and montmorillonite conserved nutrients by minimizing carbon and nitrogen losses, whereas A. oryzae enabled rapid and efficient organic fertilizer preparation by expediting humification. Under the experimental conditions of this study, the optimal additive combination was the co-application of biochar produced at 500 ℃ and A. oryzae (500CW), which can enhance the organic matter and nutrient content, increase the degree of humification, and produce high-quality organic fertilizer.