Abstract: One of key measures for preventing the invasion of termites is to apply termiticides in soil to form toxic soil layer at present. The toxic soil pillar is a main method for evaluating the effects of preventive termiticides against termites. Reticulitermes flaviceps and 20% acetamiprid SP were used in the study. The results indicated that the termite number and the food supply had significant influences on the evaluation of toxic soil pillar against Reticulitermes flaviceps, but the influence of the length of toxic soil pillar related to the concentration of acetamiprid in soil. When the length of toxic soil pillar reached 10 cm, the tested termites could not pass through the whole toxic soil pillar if the concentration of termiticide is effective to prevent the invasion of termites. In order to get the reliable data and save the time for the test, it is suggested that the length of soil pillar is 10 cm, the number of termites for every replicate is 100 termite workers, and a piece of wet filter paper is used as the food and water resource of tested termites.