The purpose of this paper was to evaluate the importance of weed control by 75% halosulfuron-methyl WG in the farming management of tomatoes was fields. The effect of 75% halosulfuron-methyl WG on the main weed control and the subsequent light penetration rate(LPR) at different heights of fields,as well as the yields of tomato were studied by means of field experiments and instrument mensuration. The results showed that:75% halosulfuron-methyl WG had significant control effects on the main broad leaf weeds and Cyperus weeds. The overall control effects of Cyperus rotundus,Amaranthus retroflexus, Melochia corchorifolia,and Acalypha australis were from 82.52% to 95.78%,and the overall quantity control effects were from 83.53% to 96.09%. The LPR in the middle and bottom of the tomato fields was significantly improved after the weed control. With weed control,the situation of light penetration rate was markedly improved,which resulted in a prominent enhancement of rice yield.