To promote the high-value utilization of Citrus sinensis Osbeck pomace, hot air drying (HAD), heat pump drying (HPD) and microwave-heat pump (MW-HPD) combined drying were used to prepare pomace powders. The effects of different drying methods on the physical properties, nutritional quality, and functional activity of the powders were systematically evaluated. Among the tested conditions, microwave pretreatment for 7 min followed by heat pump drying at 60 ℃ markedly shortened the drying time by approximately 300 min compared with conventional hot air drying, while simultaneously yielding powders with improved color characteristics and flowability. In terms of powder properties, the HPD (60 ℃) sample exhibited the smallest and most uniform particle size distribution, along with higher water-holding capacity (3.79 g/g) and oil-holding capacity (1.86 mL/g). The HAD (60 ℃) sample showed the highest bulk density (0.84 g/mL), suggesting better suitability for compression-based applications, whereas the HPD (60 ℃) sample possessed a relatively larger specific surface area, indicating its potential for use as a functional food ingredient. Regarding bioactive compounds, the MW-HPD (7 min, 60 ℃) sample showed the highest total phenolic content (9.07 mg/g), which was 53.73% higher than that of the HAD (60 ℃) sample, whereas the HPD (60 ℃) sample exhibited the highest soluble dietary fiber content (10.98%). In terms of functional activity, the HPD (60 ℃) sample exhibited strong reducing power and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging capacity, with reducing power value and DPPH radical-scavenging rate of 1.55 and 73.77%, respectively, and significantly reduced lipopolysaccharide (LPS)-induced nitric oxide (NO) production in RAW 264.7 cells (P<0.05), with a decrease of 37.4% compared to the model group, indicating notable anti-inflammatory activity. Overall, MW-HPD (7 min, 60 ℃) powder exhibited suitable characteristics for incorporation as a functional ingredient into solid beverages and various food systems, whereas HPD (60 ℃) powder, with its high specific surface area, antioxidant and anti-inflammatory capacities, was more suitable for surface adsorption in functional foods and for the formulation of functional products.