NOVELTY - Method for preparing microemulsion, involves (a) adding diethyl ether to a first stirring tank, stirring the diethyl ether, adding 2-methyl-4-chlorophenoxyacetic acid to the first stirring tank, and stirring mixture, and (b) adding water to high-speed stirring tank, stirring and adding naphthalene sulfonate to the high-speed stirring tank, stirring obtained mixture, adding tribenuron-methyl water-dispersible granules, adjusting speed of high-speed stirring tank to 210-220 rpm, slowly adding product of step (a) to the high-speed stirring tank, and stirring product.    USE - The method is useful for preparing microemulsion (claimed) which is used for controlling weeds e.g. broad-leaved weeds and annual gramineous weeds, in corn field and wheat field.    ADVANTAGE - The method is simple and environmentally-friendly to perform, requires mild reaction conditions, discharges non-polluting waste, and provides product having good quality, good dispersibility, improved penetrability, and good adhesion property.    DETAILED DESCRIPTION - Method for preparing microemulsion, involves (a) obtaining raw materials chosen from 12-14 wt.% tribenuron-methyl water-dispersible granule, 4-6 wt.% 2-methyl-4-chlorophenoxyacetic acid, 10-12 wt.% diethyl ether, 5-7 wt.% naphthalene sulfonate and water (remainder), adding the diethyl ether to a first stirring tank, stirring the diethyl ether using stirrer at room temperature and 35-40 revolutions/minute (rpm), adding 2-methyl-4-chlorophenoxyacetic acid to the first stirring tank, and stirring obtained mixture for 0.3-0.5 hours, and (b) adding suitable amount of water to high-speed stirring tank, stirring at room temperature and 35-40 rpm using stirrer, adding naphthalene sulfonate to the high-speed stirring tank, stirring obtained mixture, adding tribenuron-methyl water-dispersible granules, adjusting speed of high-speed stirring tank to 210-220 rpm, slowly adding product obtained in step (a) to the high-speed stirring tank, and stirring obtained product for 1-1.2 hours.