In this paper，1 78 plant community ~mphs collected from Maqu，South Gansu were mukivarlately nalysed by the detranded correspondence alaalysis(DCA)and the twoway indicator species analysis(TW INSPAN )，The quantitative environmental interpretation of various plant community types is given by the multivariate regression an alys is which connects the ordination scores with environmental parameters，The primary plant community types，~ological gradients，and thek quantitative relations with the environmental factors were studied．It is shown by the analysis that the vegetation types and their distribution are maily determined by the therm al and moisture gradients．They are quantitatively determined by the mathematical formu[as Which co ntains environmentaI pa rameters．