Latent heat flux (LHF) plays an important role in the global hydrological cycle and is therefore necessary to understand global climate variability. It has been reported that the near-surface specific humidity is a major source of error for satellite-derived LHF. Here, a new empirical model relating multichannel brightness temperatures ( $T_B$ ) obtained from the Fengyun-3 (FY-3C) microwave radiometer and sea surface air specific humidity ( $Q_a$ ) is proposed. It is based on the relationship between $T_B$ , $Q_a,$ sea surface temperature (SST), and water vapor scale height. Compared with in situ data, the new satellite-derived $Q_a$ and LHF both exhibit better statistical results than previous estimates. For $Q_a$ , the bias, root mean square difference (RMSD), and the correlation coefficient (R²) between satellite and buoy in the mid-latitude region are 0.08 g/kg, 1.76 g/kg, and 0.92, respectively. For LHF, the bias, RMSD, and R² are 2.40 W/m², 34.24 W/m², and 0.87, respectively. The satellite-derived $Q_a$ are also compared with National Oceanic and Atmospheric Administration (NOAA) Cooperative Institute for Research in Environmental Sciences (CIRES) humidity datasets, with a bias, RMSD, and R² of 0.02 g/kg, 1.02 g/kg, and 0.98, respectively. The proposed method can also be extended in the future to observations from other space-borne microwave radiometers.