The biological aspects and life table parameters of the spider mite, Tetranychus urticae Koch were studied under laboratory conditions on two kinds of host plants, tomato leaves and cucumber leaves. The study showed that the incubation period, the total immature stages, life cycle and generation of  T. urticae on tomato leaves were higher than them on cucumber leaves. The life cycle was 13.58 and 9.52 days on tomato leaves and cucumber leaves, respectively. The generation period was 15.91 and 11.19 days on tomato leaves and cucumber leaves, respectively. On the other hand, longevity and life span of T. urticae were higher on cucumber than on tomato. Longevity was 15.33 and 19.97 days on tomato leaves and cucumber leaves, respectively. The life span was 28.91 and 29.49 days on tomato leaves and cucumber leaves, respectively. Also, the daily main number of laid eggs was higher on cucumber, 5.36, than on tomato, 4.71.  Also, the results demonstrated that the population of T. urticae had the ability to multiply about 1.91 and 2.53 on tomato and cucumber leaves, respectively.