Abstract: To improve the efficiency of the light trap in farmland and supplies reasonable design with theory basis for the condition of farmland light traps’automation switch, this experiment set the solar light trap at tobacco or vegetable fields in southern, central and northern of Hunan, collected the important pest and natural enemies in light traps daily, and identify, counting or drying weighing; then compare the difference of insect quantity between the same sites or the different sites, and got the relationship between the major weather factors and the insect quantity by applying methods of canonical correlation analysis and regression analysis. The results indicated that the light trap catches was positively significant related to the average daily temperature (the light trap catches increased by the average daily temperature), while the light trap catches was negatively significant related to the pressure, rainfall and relative humidity (the light trap catches decreased with the pressure, rainfall and relative humidity). The warmer and drier weather conditions can improve the efficiency of light trap.