An accelerated in situ (AIS) light exposure and measurement technology for prediction of retail light protection performance of soymilk packaging is reported. The ability of a packaging material to protect light sensitive marker solutions, either comprising riboflavin (RF) or chlorophyll-a (CHLA), from an intense light source was determined. The light-induced decay of the marker was tracked with in situ spectroscopy and modeled to quantify the light protection performance of each packaging material. For a set of packages, chemical analyses (RF, thiobarbituric acid reactive substances (TBARS), hexanal) of packaged soymilk under Simulated Retail (SR) storage conditions demonstrated excellent correlation to the light protection performance data of the same package set determined by AIS (R2 > 0.97). The use of AIS enables rapid quantification of soymilk packaging material light protection performance and the associated preservation of soymilk nutrient and sensory properties, thus it may be applied to improve the design of soymilk packaging materials for light protection performance and contribute towards the improvement of packaged soymilk product shelf life.