Aphid is a major insect pest attacking ornamental plants. It causes great damage by reducing the economic values of plants. The investigated research aims to determine the relation between leaf biochemical components, morphological structures of plant leaf surface and the susceptibility of seven ornamental plants to Aphid Infestation. Highest recorded aphid infestation was observed on Tecoma stans during 2017 and 2018 seasons followed by Rosa damascena and Jasminum grandiflorum. There was no rec-orded infestation on four inspected ornamental plants, Ruta graveolens, Schefflera actinophylla, Nerium oleander and Bougainvillea spectabilis. Activity of antioxidant enzymes plays as defense line when increasing the insect population density. Biochemical components are varied among different plants that prevents or reduces insect infestation, as tannins, total phenol, and Phenol oxidase. Trichomes are considered as main morphological character in plant defense system. These results enhanced utilization resistant ornamental plants due to preventing aphid infestation. It is considered one of the integrated pest management programs, that achieves health environment without more insecticidal application.