Abstract: First of all,various approaches of classification and ordination are briefly treated.Monotheic and divisive association analysis(AA)is used for classification and more sophisticated principle component analysis(PCA)for ordination in this first paper.Computational procedures are stepwise presented in detail and computer programmes are written and deposited in the Computer Centre,Peking.Two sets of binary data are used:79 quadrats with 11 tree speicies of a Castanopsis kawakamii.forest in Central Fukien and 40 quadrats with 32 species of Aneurolipidium chinese grassland in Inner Mongolia.Results of AA and PCA agree closely to each other and also to the qualitative classification of the original authors.Aneurolepidium chinese grassland is shown clearly to have 4 discontinuous groups and its 2 and 3 dimensional ordination by PCA can retain 43.7% and 50.2% of the total information content respectively.It is,therefore,postulated that AA and PGA are complementary and very useful methods to a wide variety of ecological context,including interrelation between vegetational and enviromental attributes.