The susceptibility of Cs-based fluorides to deliquescence has led to the fact that lanthanide-doped Cs-based fluorides and their related applications have hardly been reported. Herein, the method to solve the deliquescence of Cs3ErF6 and its excellent temperature measurement performance were discussed in this work. Initially, the soaking experiment of Cs3ErF6 found that water had irreversible damage to the crystallinity of Cs3ErF6. Subsequently, the luminescent intensity was ensured by the successful isolation of Cs3ErF6 from the deliquescence of vapor by the silicon rubber sheet encapsulation at room temperature. In addition, we also removed moisture by heating samples to obtain temperature-dependent spectra. According to spectral results, two luminescent intensity ratio (LIR) temperature sensing modes were designed. The LIR mode which can quickly respond to temperature parameters by monitoring single band Stark level emission named as "rapid mode". The maximum sensitivity of 7.362%K-1 can be obtained in another "ultra-sensitive mode" thermometer based on the non-thermal coupling energy levels. This work will focus on the deliquescence effect of Cs3ErF6 and the feasibility of silicone rubber encapsulation. At the same time, a dual-mode LIR thermometer is designed for different situations.