the objective of this study was to analyze carabid and staphylinid fauna through several faunistic indexes and to obtain the population fluctuation of the dominant species in forest fragment and soybean-corn crop in no-tillage and conventional cropping system. the samplings of the coleopteran were carried out from november/2004 to april/2007, in guaíra, s？o paulo, being biweekly during the crop period and monthly in the off-season crop. for obtaining the samples it was used pitfall traps, distributed in two transects of 200 m long being 100 m in the culture and 100 m in the fragment. the fauna was characterized by indexes of diversity, equitability, and abundance. in no-tillage system the larger number of carabid and staphylinid species and the equitability and diversity indexes indicated that the community of those beetles shows a better structure when compared with the conventional cropping system. among the carabid species abaris basistriatus stood out for having been characterized as dominant in crop and forest fragment of the two experimental areas. the species scarites sp. 4 and a. basistriatus generally presented population peaks when the crop soybean counted less than 30 days of the implantation, the other species presented population peaks that were observed in varied times of the crops. pluvial precipitation was the meteorological variable that obtained the largest number of positive correlations followed by minimum temperature.