Abstract: Great changes of ecological environment have taken place in Tarim River Basin of continental river basin in arid zone since last 5 decades.As a result, a series of characteristics that are not stability appeared.With regard to the natural conditions and artificial interference, 20 complex factors of water resource system, land source system, vegetation resource system and environment system (esp.desertification state) are chosen to analyze the ecological fragility.Through establishment of indicator system of ecological fragility assessment and classification standard, based on the arithmetic logarithm processing, ecological fragility index (EFI) is built up.The results are as follows: the EFI values of source stream area including Aksu River Basin, Yerkant River Basin, Hetian River Basin and main stream including upper reaches, middle reaches and lower reaches of Tarim River Basin are 0.08, 0.23, 0.32, 0.25, 0.53 and 0.87 respectively.The degrees of ecological fragility belong to slight fragility, medium fragility and extreme fragility in Aksu River Basin, middle and lower reaches of Tarim River respectively in addition to general fragility in other three sections.

Key words: Meretrix meretrix, biomarker, integrated biomarker response index, environmental stress.