The present study was carried out to investigate the potential activity of Speedo WG 5.7% emamectin benzoate formulation (A.I) at different accelerated storage conditions to predict the stability of the formulation under storage at 54 ºC ,effect of  UV rays and effect sun light  in initial and after 3 , 14 , 21 and 35 days of exposure. Moreover to evaluate its toxicity against 4^th cotton leaf worm Spodoptera littoralis. Our results indicated that the stability of active ingredient was 5.66% in initial before exposure to different storage conditions.In the treatment of temperature at 54 ºC the stabilities were 5.50 , 4.71 , 3.93 , and 3.55 % after exposure to ultraviolet rays they were 5.46 , 5.05, 4.22 , and 3.73 %, while after exposure to sunlight were5.03 , 4.94 , 3.78 ,and 3.42% after 3-14 -21-35 days , respectively. Storage for a period of 45 days, was decomposed about 50%(TD50) of the active ingredient in the formulation at 54ºC reached to 48.47% ,to 53.57%under  ultraviolet rays and under direct sunlight was 51.43 %. The toxicity results showed that the LC_50s of Speedo formulation recorded14.957mg/l at initial, and 35.097, 71.040, 160.307, 429.257mg/l after 54 ºC  temperature,22.580, 36.329, 59.431, 91.568 mg/l after exposure to UV and(51.935, 90.601, 233.491, 2432.3) mg/l after the treatments of the exposures to direct sunlight.