Mosses play a pioneer role in succession series in terrestrial ecosystems and thus present important ecological functions. After long-term evolutionary adaptation, mosses have formed certain morphological, physiological, and genetic regulatory strategies to avoid adverse conditions. Mosses live in complex and diverse microhabitats, among which shaded and exposed habitats are the two most common types. Differences among these microenvironments are mainly reflected in changes in water, temperature, and light. In contrast to other substrates, rocks inhabited by saxicolous drought-tolerant mosses are absolutely dry substrates with strong daily variations in surface temperature and ineffective water retention. These characteristics present great challenges to the survival of saxicolous drought-tolerant mosses. The moss Grimmia pilifera is a model drought-tolerant moss that is widely distributed in China. It generally grows on exposed rock surfaces with variable microhabitats. Its growth is affected by the interaction of water, light, and temperature. However, we know little about how its photosynthetic characteristics respond to varied environmental conditions. In this study, in situ (exposed and shaded microhabitats) and indoor simulation experiments were carried out to test the effects of different water (simulated precipitation and precipitation frequency) conditions, light, temperature, and their combined gradients on the chlorophyll fluorescence characteristics of G. pilifera. The results of the in situ experiment showed that the photochemical efficiency of G. pilifera in the in situ shaded habitat was significantly higher than that in the exposed habitat. Under the same indoor culture conditions, the duration of the effective photosynthetic efficiency of moss individuals in the shaded habitat during dehydration was obviously shortened compared with that of moss individuals in the exposed habitat, indicating reduced dehydration tolerance. The combined simulation experiment on water, light, and temperature showed that precipitation frequency and light temperature exerted highly significant effects on the photochemical efficiency of G. pilifera and exhibited a certain interaction. However, precipitation (water quantity) had a weak influence. G. pilifera showed the highest photochemical efficiency under the conditions of low light temperature and/or the precipitation frequency of one time per 2 days. Consequently, shaded habitat, low light temperature, and moderate precipitation frequency were conducive to the growth of G. pilifera. However, G. pilifera in the exposed habitat had stronger environmental tolerance than G. pilifera in the shaded habitat. This characteristic indicated that once the shaded microenvironment is destroyed (for example, through the death and removal of vascular plants), mosses in this habitat will face a severe test of survival. In addition, our results also revealed that low-light and low-temperature conditions and moderate simulated precipitation frequency were beneficial to the individual growth of G. pilifera, showing certain indicative importance for indoor culture research.