In order to make the research on the design of locusts’ LED trapping light and digital control of induced light field by utilizing LED light source and homemade phototactic behavior trial equipment, the comparative tests of locusts’ phototactic behavior for the choice of purple light, purple-blue-green light in different time periods were carried out by adopting contrast experimental method. The reason affecting locusts’ phototactic behavior was analyzed. The results suggested that locusts’ phototactic choosing behavior was relevant with spectrum, illuminance gradient, internal biological features and environmental factors under the same illuminance gradient. Locusts’ phototactic behavior choosing purple light was higher than purple-blue-green, under the different illuminance gradient. Locusts tended to select the stronger illuminance gradient. When the illuminance gradient of purple-blue-green was 10 times higher than purple light, locusts’ selective response to purple-blue-green light was superior to purple light. Locusts’ internal biological features and environmental factors restricted the increasing effect of locusts’ phototactic behavior by improving light intensity in the different time periods. The sensitive degree of locusts’ phototactic response to purple light as well as purple-blue-green light at night was different, locusts’ phototactic behavior showed that locusts’ phototactic sensitive critical point, the optimal and the best range of light illuminance values, locusts responding to purple light as well as purple-blue-green light in the different time periods of night, was different.