To investigate the effects of freeze-thaw cycles (FTCs) on microbial carbon-source metabolism and diversity in black soil farmland in Northeast China, soil physicochemical properties were measured, and MicroResp™ was used to characterize microbial carbon metabolic activity and its relationship with soil physicochemical properties under different freeze-thaw frequencies (1, 3, 5, 9, and 17 cycles; designated as 1FTC, 3FTC, 5FTC, 9FTC, and 17FTC, respectively) and freezing temperatures (−9, −18, and −26 ℃). The results showed that total microbial carbon metabolic activity was significantly influenced by FTC intensity. At 1FTC, 3FTC, and 5FTC, soils subjected to −9 ℃ showed higher metabolic activity than those subjected to −18 ℃; however, at 17FTC, the metabolic activity at −9 ℃ was lower than that at −18 ℃. Moreover, at 5FTC, metabolic activity at −9 ℃ was lower than that at −26 ℃. Microbial carbon-source utilization patterns also shifted with freezing temperature. During FTC, microorganisms primarily utilized carbohydrates and carboxylic acids, whereas utilization of amino acids increased as freezing temperature decreased. As the freezing temperature decreased, soil microbial diversity and evenness showed a trend of first increasing and then stabilizing at 5 FTC, first decreasing and then stabilizing at 17 FTC, and first increasing and then decreasing under other freeze-thaw frequencies. Diversity also fluctuated markedly with increasing FTC frequency at −26 ℃. Principal component analysis indicated that FTC intensity significantly affected microbial carbon metabolic activity and community structure (P<0.01). In addition, random forest analysis and partial least squares structural equation modeling showed that FTC significantly altered soil physicochemical properties, particularly soil water content, nitrate nitrogen, total nitrogen, and soil organic carbon, thereby regulating microbial carbon metabolic activity. In conclusion, moderate FTC frequency under mild freeze-thaw intensity promoted microbial diversity and enhanced carbon metabolic activity, whereas high-intensity and high-frequency FTC inhibited microbial metabolic function by altering soil physicochemical properties.