As an alternative of traditional compacted clay layer,sodium bentonite geosynthetic clay liner(hereinafter referred to as GCL) has excellent performance of anti-seepage and isolation, hence has been widely used in the anti-seepage engineering of water conservancy, environmental protection, transportation and other fields. GCL has been applied in China for over two decades, but misunderstandings about GCL still exist, which hinders the further application of GCL. In this article, problems of GCL, inclusive of the flatness of geo-woven, the performance of bentonite, the cognition and the testing methods, are expounded according to our experiences in GCL production and research for over a decade. Results suggest that uneven geo-woven is not available for producing GCL; powdered GCL should be selected for project with GCL as a main impermeable layer; although as a secondary barrier layer in environmental projects, GCL is an important part of the whole anti-seepage system; detection of flatness and leakage should be included and also the early hydraulic conductivity of GCL should be reflected in the testing standards of GCL.