Abstract: White fly is one of the main pests in greenhouse. In order to reduce the damage of chemical pesticides to human being and enhance the safety of the product, the pilot studies have been done with natural enemy and physical preventative method. Four aspects have been involved in this test. They are the optimal applied time and the optimal density of Encarsia Formosa, the optimal hanging height and preventative result of the yellow board. The test result shows that greenhouse white fly can be controlled by continuously applying Encarsia formosa Gahan twice when the density of white fly in greenhouse is two plants have one pest. The optimal density is 150000 Encarsia formosa Gahan per hectare every time and the availability is about 95.6%. The yellow boards play an important role in prevention and cure white fly in greenhouse because they can trap, stick and kill white fly. The test also shows that almost white fly often appear in the space where 5cm-15cm upper than the top of the plant. According to this result, the optimal hanging height of the yellow board should be at the place where 5cm-15cm upper than the top of the plant. The yellow boards should be set up as much as possible in this space to reach the best preventative effect.