Trifolium repens Linn. is one of the familiar herbs in agricultural production and it is significant to study how to control it. Effects of physiology and biochemistry of the mixture of fluroxypr mepthyl and paraquat(4∶1, the proportion of effective ingredients) against T.repens were studied with pot screening,including conductivity,oxygen free radical produced rate,acetolactate synthase(ALS) activity and so on,with fluroxypr mepthyl and paraquat as controls. The results indicated that the mixture treatment showed very strong synergism against T.repens' conductivity and oxygen free radical produced rate,which the M value of the actual to the theoretical inhibition ratio of conductivity was 789.44 after 2 days treatment and the M value of the actual to the theoretical inhibition ratio of oxygen free radical produced rate was 262.12 after 4 days treatment. The addition function was also displayed on ALS activity with the M value of 104.12 after 2 days treatment. Therefore,the synergism proportion is worthy of a further study.