The paper applies niche theory and niche model in ecology to study the characteristics and regularity of enterprise niche, reveals that the essence of relation between enterprises is the relation of enterprises niche. Establish and analyze the model of niche, diversification, separation of enterprises and the model of relationship between competition repel with environment changes etc., analyze the principle of competition repel and evolution of enterprise niche. Provide new way of thinking on niche in ecology for management of enterprises, so that the decision of enterprise would be more scientific and correct, the relation between enterprises would be more harmonious.