Abstract: The niche of seven dominant spiders in cotton field is analyzed in this paper．According to temporal niche，horizontal spatial niche，vertical spatial niche and temporal-spatial three-dimensional niche，the quantitative estimation of niche breadth and overlap is done also．The results show that the temporal niche breadth value of Pardosa astrigera(0.9218)is maximum，that of Dictyna arundinacea(0.9176)is the second，and the temporal niche overlap values of Misumenops tricuspidatus and Chiracanthium japonicum (0.8083)are maximum．The horizontal spatial niche breadth value of Neoscona doenitzi(0.4307)iS minimum，and others are focused between 0.8814～0.9912，and their horizonta1 spatia1 niche overlap values are focused between 0.7200～0.9500．The vertical spatial niche breadth value of Erigondium gramincola (0.7998)is maximum and the vertical spatial niche overlap values of Erigondium gramincola and Achaearanea tepidariorum (0.7600)are maximum．The three-dimensional niche breadth value of Erigondium gramincola(0.7189)is maximum and the three-dimensional niche overlap values of Erigondium gramincola and Achaearanea tepidariorum (0.3716)，Chiracanthium japonicum and Dictyna arundinacea(0.3715)，Erigondium gramincola and Chiracanthium japonicum (0.3695)are biggist．On the basis of three-dimensional niche overlap value，one competition guild is made out，including Erigondium gramincola，Chiracanthium japonicum ，Achaearanea tepidariorum and Dictyna arundinacea．