The quasi-biweekly oscillation (QBWO) in the South China Sea (SCS) influences the weather and climate of the surrounding area directly by modulating the sea surface energy flux, which has not been fully understood due to the scarcity of observation. The QBWO signals were filtered from the outgoing longwave radiation (OLR). Then, we quantified the response of sea surface energy fluxes onto QBWO in the SCS from May to July 2019 by using the underway observation on the research vessel SHENKUO and the ERA5 reanalyses. The anomalies of surface downward and upward shortwave fluxes and downward longwave radiation fluxes are 25.61, 1.48, and 2.41 W m^-2, respectively, and their spatial patterns are pretty identical with QBWO, centered within 10° - 20°N, 110°-125°E. There were weak and insignificant responses in both SST and its controlled surface upward longwave radiation during QBWO. The spatial patterns of both surface sensible and latent heat fluxes’ anomalies differed from radiation fluxes. The sensible heat flux’s anomaly mainly centered around 8° - 20°N, 115°-120°E, being about 3.08 W m^-2; while that for the latent heat flux centered at 8° - 20°N, 105°-125°E, being 18.31W m^-2. The mechanism behind these different responses has also been discussed.