Abstract: The sodium bentonite geosynthetic clay liner (hereinafter short for GCL) has been applied for over twenty years in China. However, there are some important negligences in the production and applications of GCL, and its anti-seepage performance is affected. The factors such as type of woven geotextile, particle size of bentonite, overlapping in construction as well as some issues in the test methods are analyzed, and their effects on the test methods and anti-seepage performance of GCL are clarified. The results show that the circular woven geotextile is not suitable for producing GCL. The right kinds of GCL should be selected according to the project. For example, while using GCL as the main impermeable layer, powdered GCL should be chosen. GCL construction should strictly follow the installation guide, handling the overlapping area should be standardized and reliable, and the most crucial of overlapping is to stop the drainage effect of nonwoven geotextile. The dead zone of the relevant standards should be improved.