Gigantopithecus blacki is the largest hominoid with massive jaws and thick tooth enamel in the world and lasts from the early Early Pleistocene to the middle Pleistocene in South China. Understanding its foraging ecology is vital to unlocking the mysteries of its survival, evolution, and extinction. Although many analytical methods have been applied to reveal its foraging ecology, there is still a lack of direct evidence on the trophic level of G. blacki. For the first time, we presented the Ca isotope data of Gigantopithecus fauna at the locality of Liucheng Gigantopithecus Cave (～2 Ma), Guangxi, China during the early Early Pleistocene. The isotopic pattern from herbivores to carnivores is following the general trophic rule, i.e., the step decrease of δ44/42Ca values alongside the food chain. However, the cervids and Stegodon have extremely low δ44/42Ca values that are close to carnivores (hyenas) while G. blacki and Ailuropoda have the highest δ44/42Ca values among animals. When compiling the isotopic (δ13C, δ18O, δ44/42Ca) data together, we distinguish the animal niches well. Considering the dietary and physiological factors to influence δ44/42Ca values in diets, we suggest that cervids and Stegodon could have consumed lots of grasses and/or bones as an additional mineral supplement and that G. blacki and giant panda might have fed on C3 plant leaves and/or minerals from soils or rocks. The comparison of δ44/42Ca values among G. blacki, modern primates, and hominins indicates the significantly highest δ44/42Ca values in G.blacki in Asia and Paranthropus boisei in Africa. Even though both animals have distinctive δ13C and δ18O values, they have quite close δ44/42Ca values, suggesting a possible shared similar mechanism of Ca fractionation. Finally, the implications of δ44/42Ca values to reveal animal diets and physiology on species-specific scales were discussed. We hypothesize that foraging on mineral licks from soils or rocks could have been one of the main driving factors to account for the high δ44/42Ca values in the enamel of G.blacki, P. boisei, and giant panda, which possibly meets physiological demands to adapt to chew hard foodstuffs. Our study provides novel insights into the uniqueness of G.blacki's foraging ecology and displays the complexity of Ca isotope values to decipher animal diets and physiology.