This study was conducted to evaluate the effect of intercropping and potassium fertilization for maize with cowpea plants on the population density  levels of some piercing –sucking insects at Diarb Negm distract in Sharkia Governorate during 2009 and 2010 seasons. The obtained results showed that intercropping system (3:3) maize with cowpea decreased Rhopalosiphum maidis (Fitch), Rhopalosiphum padi(L .) , Aphis gossypii (Glover), Empoasca decedens (Paoli),   Empoasca decipiens(Paoli)  , Cicadulina chinai (Ghauri)  andwhitefly Bemisia tabaci (Genn.).  Whereas, increased average numbers of planthopper  Sogatella vibix (Haupt) andSogatella furcifera (Horv.) in both seasons . The results indicate that increased of yield in the solid system but insignificantly with intercropping   system (3:3). Data presented clearly that rate of 100 kg of potassium fertilization / fed. gave increased of yield maize with cowpea plants and decreased infestation of sap-sucking insects in both seasons. Lysiphlebus fabarum (Marshall) was the singe primary parasitoid species emerged from Aphis craccivora (Koch.) mummies Also, Diaeretiella rapae (M' Intosh) was the primary parasitoid emerged from R. maidis mummies and Praon sp. was the primary parasitoid emerged from R. padi mummies. The mean percentage of parasitoid were 5.52 ± 2.02 and 4.33 ± 1.58 in (L. fabarum), 1.21 ± 0.43 and 1.71 ± 0.46 (D. rapae) and it were 1.38 ± 0.53 and 1.11 ± 0.35 (Praon sp.) in both seasons respectively. Five predators were associated with these insects on cowpea crop. These predators were Coccinella undecimpunctata (L.), Cydonia vicina isis, Cy. vicina nilotica, Metasyrphus corolla (F.) and Chrysoperla carnae (Steph). Meanwhile three predators were associated with these insects on maize crop. These predators were C.  undecimpunctata, M. corolla (F.) and C.  carnae.