population fluctuations of certain mites associated with soybean and cotton plants were investigated during seasons, 2012 and 2013 at Sharkia Governorate, as well as its relation with some prevailing climatic factors. In soybean plants, the population of phytophagous mite, Tetranychus urticae Koch was recorded in high number in 2nd season than the 1st one, whereby represented by 272.83 and 202.69 individuals, respectively. While, the predacious mite, Phytoseiulus macropilis (Banks) recorded in high number in 1st season than the 2nd season were aggregated 37.72 and 25.91 individuals, respectively; on soybean plants. The population of T. urticae was higher in 1st year than the 2nd year (394.92 and 367.65 individuals, respectively; while the predacious mites were high in the 2nd year than that obtained in the 1st one on cotton plants. These results revealed that there is negative significant relation between the predacious mite species and the phytophagous mite species on soybean and cotton plants. The population of the spider mite T. urticae was significantly related to the leaf contents of protein and phosphorous, while there was no significance between the predator (P. macropilis) with leaf phytochemical contents of soybean during two seasons 2012/13. The population of the spider mite and leaf phytochemical contents of cotton during season 2013 revealed that there is highly significant correlation between the pest mite T. urticae with protein, carbohydrate, total sugar and reducing sugar, while there was no significance between the pest and non-reducing sugar. The population revealed that there is no significant correlation between the predator Typhlodromus californicus withprotein, carbohydrate, reducing sugar and non-reducing sugar. The correlation coefficient was significant between the predator Agistemus exsertus and carbohydrate, total sugar and reducing sugar, they also recorded a highly significant correlation between the predator and protein; while there was no significance difference between the two predators (A. swiriskii & E. scutalis) with phytochemical contents