During the past three decades, maize yields in China have steadily increased as producers experienced climate changes and utilized improved hybrids and management, etc. Elucidating the relative contributions of these factors to historical yield changes will aid in sustaining or increasing yields in the future. In this study, statistical methods were used to estimate the contribution of incident solar radiation to maize yield trends in five climate zones in China from 1985 to 2014. This study analysed the direct effect of solar brightening or dimming assuming a constant grain filling period (GFP) typical for 1985. We also evaluated the interaction between solar brightening (or dimming) and increases in the length of the GFP (LGFP) through crop improvement from 1985 to 2014. The results showed that solar brightening during the GFP contributed to 5.9% of the yield increase over the past three decades, primarily due to increases in diffuse radiation in various locations. The contribution of the daily solar radiation intercepted during the GFP to yield trends varied among climate zones; in humid warm temperate and arid warm temperate zones, daily solar dimming caused yield decreases in some of the locations. Nevertheless, combined with a prolonged LGFP, the increased solar radiation accumulation during the GFP ameliorated the negative effects of solar dimming, resulting in significant maize yield gains. Therefore, increased solar radiation accumulation during the GFP contributed to approximately 28.8% of the maize yield increase in China from 1985 to 2014.