The niche breath of Aphis citricota and Tetranychus viennensis were more than other pests in U.S.apricot and plum orchard,those are dominant population occupying more space;Resources of natural enemies were rich and majority was Chrysopa septempenctata;Pests had strong competition,natural enemies were so.Natural enemies and major pests could meet very often.They had strong pursuing and control effect to Aphis citricota and Tetranychus viennensis from time dimension.The follow orders of the number of main natural enemies and main pests Aphis citricota was chrysopidaes>Propylaea japonica>araneidas>Leis axyridis>other coccinellidaes>syrphidaes>Coccinel laseptem punctata>Hippodamia variegata.The fuzzy neartude of chrysopidae and Propylaea japonica were highest than others,that two and Aphis citricota have the highest relations of same domain,and stong to pursue Aphis citricota,to inhibit the number of Aphis citricota.