Surface shortwave radiation (SSR) plays an important role in global energy systems. The new generation of geostationary meteorological satellite Himawari-8, with higher spatiotemporal and spectral resolution, offers a new opportunity to retrieve SSR with higher accuracy. In this study, an improved algorithm was applied to estimate instantaneous, hourly, and daily mean SSR using cloud products from the Advanced Himawari Imager (AHI) onboard the Himawari-8 satellite. The validation against Baseline Surface Radiation Network (BSRN) stations showed a root mean square error (RMSE) of 95.8 W m−2 for instantaneous SSR, 82.4 W m−2 for hourly SSR, and 22.8 W m−2 for daily SSR and mean bias error (MBE) of −15.8 W m−2, −14.1 W m−2, and −6.6 W m−2. The validation against China Meteorological Administration (CMA) stations showed a RMSE of 99.5 W m−2 and MBE of −8.2 W m−2 for hourly SSR and RMSE of 27.7 W m−2 and MBE of −3.9 W m−2 for daily SSR, which are generally better than the Himawari-8 SSR product. Overall, the improved algorithm performed well on the new-generation geostationary satellite, with high accuracy and efficiency, and would contribute to surface process research and photovoltaic engineering applications.