Abstract: Analysis on the harmfulness of toxin produced by Penicillium purpurogenum in soil in the whole growth and development period of continuous cropping soybean shows that the toxicity began at the stage of seed germination.At the seedling and branching stages, high toxin concentration (1000 delution folds) could entirely result in non-nodulation, and even low concentration (100000 delution folds) could still inhibit 40% of nodulation, resulting in an obvious decrease of photosynthetic and nitrogen-fixing capacities of continuous cropping soybean.By stimulating the growth of P.purpurogenum, the root residue and litter of soybean could cause further harmfulness of soybean.Studies on controlling toxin of P.purpurogenum in soils of continuous cropping soybean show that soil actinomyces MBantibiotic control could make continuous cropping soybean have a yield increase of 8.4～18.9%; and marine actinomyces MB-97 biotic control could make a yield increase of 30.5%.With the application of MB 97 bio fertilizer and comprehensive control on disease precaution and toxicity reduce in the whole growth and development period of continuous cropping soybean, the yield of continuous cropping for 5years in micro-plot field experiment could reach 4575kg·hm^-2 .

Key words: Soybean, Continuous cropping obstacles, Toxin of Penicillium purpurogenum, Control techniques