Pak-choi, a variety of Non-heading Chinese cabbage, is a crucial leafy vegetable crop in Taiwan's northern regions, particularly in protected cultivation systems. In recent years, extreme weather conditions have negatively impacted its growth, emphasizing the need for breeding heat-tolerant varieties capable of rapid growth under high-temperature conditions to mitigate losses. High-throughput phenotyping offers a rapid, standardized, and non-destructive method for collecting plant traits, facilitating the establishment of phenotypic databases to accelerate the breeding process. This study utilized six commercial varieties of Pak-choi and employed the high-throughput phenotyping tool, Trait Finder, to collect phenotypic data. The results demonstrated that the collected phenotypic parameters were quantifiable and reflected the effects of heat stress on plant growth. Notably, significant changes in 3D leaf area and digital biomass were observed starting from the ninth day of heat stress treatment, suggesting a positive impact on early-stage heat stress screening for this crop. Furthermore, in the development of heat stress screening indicators, the study identified correlations between four vegetation indices and leaf area/digital biomass. Among these indices, the Plant Senescence Reflectance Index (PSRI) exhibited the highest correlation, surpassing the other three indices in its effectiveness.