<p>The study employs synthetic analysis, empirical orthogonal function (EOF), correlation coefficient analysis, and causality analysis to investigate relationships between radiation flux and El Niño and Southern Oscillation (ENSO) in the tropical Pacific over the past 170 years. Our results indicate that Surface Downwelling Longwave Radiation (SDLR) increased significantly, by about 0.05&#xa0;W / (M² * a), TOA Outgoing Longwave Radiation (TOLR) decreased slightly, by about 0.02&#xa0;W / (M² * a), Surface Downwelling Shortwave Radiation (SDSR) did not change significantly, and TOA incident shortwave radiation (TISR) increased slightly, by about 0.001&#xa0;W / (M² * a). In the tropical western Pacific, the average state of atmospheric rising and sinking intersecting area shifted eastward by 0.05 ° / a, and El Niño Modoki events increased. In the central-eastern Pacific, particularly in regions with ocean depth greater than 700&#xa0;m within the Niño 3.4 zone,, ocean heat content increased significantly, the location of the maximum Isothermal Layer Depth (ILD) shifted eastward, convective activity in the intersecting area was abnormally enhanced, the frequency of westerly wind bursts decreased, and the probability of El Niño Modoki occurrence increased. There was a causality relationship between marine heat content and radiation flux, vertical (w), zonal (u), and meridional (v) wind anomalies near the rising and sinking intersecting area. When the time series of the factor advanced or delayed, the correlation coefficient generally increased. Also, causality analysis confirmed a causal relationship between TOLR, SDLR, and the location of the maximum ILD. The location of the maximum ILD and marine heat content in Niño 3 zone (H_niño3) and Niño 3.4 zone (H_niño3.4) interact as both cause and effect. The innovation of this research lies in exploring ENSO evolution through centennial-scale radiation changes and applying causality analysis to the study of its physical mechanisms.</p>