To evaluate the impact of climate change on maize production, accurately measuring the radiation use efficiency (RUE) of maize is critical.  This study focused on three maize cultivars in Jilin Province, China: Zhengdan 958 (ZD958), Xianyu 335 (XY335), and Liangyu 99 (LY99).  Under the optimal growing conditions for high density planting (9 plants m^–2), the maize RUE was determined during the vegetative and reproductive phases, and the entire growth period.  The results showed that the canopy light interception for maize peaked during anthesis.  After anthesis, maize plant biomass continued to accumulate.  The maize RUE was calculated based on the absorbed photosynthetically active radiation (APAR).  During the entire growth period, maize RUE averaged 5.71 g MJ^–1 APAR among the three cultivars, with a high-to-low order of ZD958 (5.85 g MJ^–1 APAR)>XY335 (5.64 g MJ^–1 APAR)>LY99 (5.07 g MJ^–1 APAR).  Within the vegetative and reproductive growth periods, maize RUE averaged 6.85 and 5.64 g MJ^–1 APAR, respectively.  When utilizing maize models that depend on RUE to predict aboveground biomass accumulation, such as APSIM, the current RUE value of 3.6 g MJ^–1 APAR is considerably lower than the measured value obtained under high-density optimal growing conditions.  Consequently, to derive the optimal potential yield for maize in such planting conditions, we recommend adjusting the RUE to a range of 5.07–5.85 g MJ^–1 APAR.