Laccases are extensively used in the textile industry due to their ability to decolorize dyes, modify fabric surfaces, and bleach textiles. Identifying a laccase with both high thermal stability and alkali tolerance suitable for textile applications presents a significant challenge. A novel alkaline laccase, LacCT, was discovered from Caldalkalibacillus thermarum and successfully expressed it in Escherichia coli. LacCT displayed optimal activity at 65°C and maintained high stability across a pH range of 6.0–10.0, with an optimal pH of 7.5. Through rational design, the thermal stability of the best variant, G190P/Q254Y/G336M/D510F (LacCT‐11), was significantly enhanced, resulting in a half‐life of 63.2 min at 60°C – 1.8 times longer than that of the wild type. This research introduces a promising new laccase with considerable potential for decolorizing textile wastewater and improving the ramie degumming process.