The present study aimed to clear the fluctuation dynamics for both Tetranychus urticae Koch and the associated predatory mite Amblyseius gossypii ElBadry to show their active periods that advantageously in controlling T. urticae biologically. It was occurred on guava trees (Psidium guajava L). Guava trees were seven years old in an orchard in Beer El-Abd city, North Sinai Governorate, Egypt were studied during April 2019 to March 2021. Observation was done fortnightly on both mite species density per leaf by selecting ten guava trees each of four accessions and five branches from each plant with the help of 20x hand lens. Both year the population of T. urticae showed its highest density through two essential periods in early and mid- summer, while the predatory mite, A. gossypii began its activity with the beginning of the prey activity. At winter season, the population of both the prey and the predator dropped.