Abstract: In order to determine the suitable application condition of tembotrione, the effects of simulated rainfall, light intensity, temperature, and application period on its herbicidal activity against Digitaria sanguinalis were compared in the greenhouse, and the weed control spectrum was determined. Meanwhile, the field weed control efficacy and the safety to maize ‘Xundan 20’ were evaluated at different leaf stages. The results showed that there was no significant difference in the fresh weight inhibition to D. sanguinalis when the simulated rainfall happened at 4 h after tembotrione application with the doses (active ingredients, the same below) of 27, 54, and 108 g/hm². The efficacy of tembotrione against D. sanguinalis under full light (100%) was significantly higher than that under medium light (48%) and low light (9%). In the temperature range of 20-35 ℃, the efficacy of tembotrione against D. sanguinalis was higher than that in 15 ℃/20 ℃. The efficacy of tembotrione against D. sanguinalis at 1-4 leaf stages was significantly higher than in other stages. At the same time, at the dose of 216 g/hm², the inhibition rate to fresh weight of maize over-2 leaf stage was less than 0.33%. At the dose of 108 g/hm², the inhibition rates to the fresh weight of Echinochloa crus-galli, Eleusine indica, Commelina communis, Setaria viridis, Chloris virgata, Leptochloa chinensis, Celosia argentea, Acalypha australis, Abutilon theophrasti, Ludwigia prostrata, Eclipta prostrata, and Cyperus iria were more than 91%. The field trial results showed that 42 days after application at the 3-4 leaf stage of maize, the total fresh weight control efficiency of tembotrione to weeds at the dose of 126 g/hm² was 88.68% and the yield increase rate of maize was 24.31%, which were higher than those (78.37% and 14.96%) at 6-7 leaf stages. The total fresh weight control efficacy of mesotrione to weeds at the dose of 150 g/hm² was 76.32%. In conclusion, the optimum time, temperature, and light intensity for tembotrione to exert the best efficacy were at 1-4 leaf stage of the weeds on sunny days, temperature higher than 20 ℃, and over 2 leaf stage of the maize.