Abstract: Abstract: Much more Kitchen Wastes (KW) have been generated and collected separately, as the proposals for the practice of waste separation in China. Among them, bio drying is an emerging technique to remove water from biodegradable wastes. However, the KW bio drying is also confined to the application in practice, due to the long treatment cycle, low temperature and dehydration efficiency. In this study, a thermally assisted bio-drying system was established and developed to fully meet the market demand for better performance and high efficiency of water removal. The air-flow rate and bulking agent were the most important factor for the traditional bio drying process. But there were few reports about the sole and synergetic effect on the thermally assisted bio-drying process. Therefore, a comparison was then made to clarify the influence of aeration volume and particle size on the auxiliary heat biological drying, particularly for the low consumption of energy efficiency and high bio drying efficiency. Three aerations (0.4, 0.6, and 0.8 L/(min·kg)) and different particle sizes of auxiliary material (coarse particle size > 15.0 mm, fine particle size < 5.0 mm, and mixed particle size 5.0-15.0 mm) were set for the factorial experiments, in order to explore the biological drying efficiency for the kitchen wastes. Some bio drying parameters were determined to assess the bio drying performance. The flow balance of energy and water in the system was calculated to further assess the water removal and energy utilization rate. The results show that the aeration rate posed a greater effect on the bio drying temperature and water removal, compared with the particle size. A better performance was achieved, particularly for the higher heating rate and the longer duration at the high-temperature stage, and the higher effective accumulated temperature under the 0.6 L/(min·kg) aeration. The high-temperature stage of auxiliary heat bio drying was more than seven days, except for the treatment with the 0.4 L/(min·kg) and fine particle size. The treatment of 0.8 L/(min·kg) and fine particle size performed the best for the water removal. Specifically, the highest bio drying index was 4.0, the final water content was 17.0%, and the water removal rate was 95.8%. The energy and water balance show that evaporation was the main way of water removal in the bio-drying process, accounting for 40%-80% of the total water removal. The main input energy was the heat production of biomass (63.0%-73.0%), whereas, the main output energy was the latent heat of evaporation (26.0%-46.5%) and reactor heat loss (28.3%-49.4%). The highest energy utilization efficiency was achieved in the treatment with the 0.8 L/(min·kg) and fine particle size, up to 65.1%. The latent heat of evaporation accounted for 48% of the output energy in the treatment with the 0.8 L/(min·kg) and fine particle size. However, the pH value and germination index in the treatment with the 0.4 L/(min·kg) and fine particle size failed to meet the compost safety and maturity standards after 16 days of bio drying by auxiliary heat. Therefore, the fine particle size of bulking agents with a higher aeration rate (≥0.6 L/(min·kg)) can be expected for the bio drying process with the auxiliary heat for KW for better bio drying and energy utilization efficiency.