Shotcrete cracks are common in tunnels in high temperature and high humidity environments. Therefore, to investigate the mechanical evolution patterns of shotcreting materials in tunnels in high temperature and high humidity environments, a calculation method for tunnel support structure load considering thermal coupling effect is proposed. To minimize the impact of high temperature and humidity on concrete materials, a design method for fiber reinforced shotcrete is proposed. This design includes material mix proportions and auxiliary cooling measures for materials and environment. Moreover, a crack evaluation method for tunnel shotcrete in high temperature and high humidity environments is established based on theoretical derivation, and onsite crack inspection of steel fiber shotcrete is conducted based on theoretical analysis. The results indicate that after reasonable design of the tunnel shotcrete mix ratio, the crack width of steel fiber shotcrete 〖WT〗w〖WT《TNR》〗 is 0.14 mm, which is smaller than the crack limit width〖WT〗 wmax 〖WT《TNR》〗of 0.2 mm, meeting safety regulations. Thus, the fiber reinforced shotcrete and auxiliary cooling measures can effectively control the development of cracks in tunnel shotcrete in high temperature and humidity environments.