The karst dammed lakes in limestone area of Minshan Mountain Range, NW Sichuan, belong to a special kind of lake morphology. They developed and were formed under certain geological, geomorphological and hydrochemical conditions with bio-effects as result of rapid tufa dam gradation in stream channel. With field observation on the sedimental structure, lake morphology and water chemistry as well as optical & Scanning Electronic Microscopic observation on tufa samples from the research area, various kinds of bio-effects have been identified to exist in the process of tufa dam formation. It is shown in the general cycle model proposed in this paper that many organisms (mosses, algae and bushes etc.) with various effects (assimilation, interceptionr capillary effects trapping & bindings and shoring effect) on tufa deposition play an important role throughout the compound cycle process of tufa dam gradation (i. e. the formation of karst dammed lakes) in the stream channels in the research areas.