The invention relates to an agricultural chemical composition, particularly to a weeding and synergistic composition for controlling wheat field weeds. The weeding and synergistic composition for wheat fields consists of cyanazine, mesosulfuron-methyl and a corresponding assistant and/or a filler, wherein the sum of the cyanazine and the mesosulfuron-methyl accounts for 10%-90% of the total weight of the composition, and the cyanazine and the mesosulfuron-methyl are in a weight ratio of 10:0.05-2. The cyanazine is very different from the mesosulfuron-methyl in terms of mechanisms of action and weed control spectrums, etc, and blended use of the two can achieve strong complementarity. With the advantages of substantial synergistic effect, weed control spectrum expansion, drug resistance delaying and the like, the weeding and synergistic composition provided in the invention especially has very good activity on Aegilops tauschii, wild oats and other gramineous weeds.