Laccases have a wide range of uses in the textile industry for their ability to decolorize dyes, modify the surface of fabrics and bleach textiles. Screening a laccase with high thermal stability and alkali tolerance suitable for textile applications is challenging. In this study, we identified a novel alkaline laccase, LacCT, from Caldalkalibacillus thermarum, and expressed it in Escherichia coli. It showed an optimal temperature of 65°C and a pH range of high stability from 6.0 to 10.0, with an optimum pH of 7.5. Through rational design, the thermal stability of the best variant, G190P/Q254Y/G336M/D510F (LacCT-11), was significantly improved, exhibiting a half-life of 63.2 minutes at 60°C, 1.8 times longer than the wild type. This research presents a new laccase with significant potential for decolorizing textile wastewater and enhancing the ramie degumming process.