The field surveys were investigated on the rate of infected moths of Spodoptera litura by Nosema sp. At Can Tho city. Additional, two experiments were conducted to inoculate the concentrations of Nosema sp. on the second instars of S. litura and on Anabas testudineus, The result of field survesy showed that above 40 percent of the moths of S. litura on the field was infected by Nosema sp. in the condition of laborator, all the second instars of S. litura were infected by Nosema sp. from the concentration of 105 to 109. Furthermore, the concentration at 109 spore/mL have had the highest effectiveness over 84 percent (at 15 days after inoculation) on the second instars. The Nosema sp. is not almost affected to the growth of Anabas testudineus and the environmental actors.