The invention relates to a weeding water aqua prepared by binary combination of gramoxone and 
MCPA-Na and preparation method thereof. The weeding water aqua is composed of the following components by 
mass percent: 3-10% of gramoxone, 2-10% of 
MCPA-Na, 0.01-0.3% of 2-Amino-6-methyl-4-propyl-1, 2, 4triazolo [1,5a] pyriin-5(4H)-on, 5-15% of synergist, 8-20% of penetrant, and 
balance water. The preparation includes that: in the 
mass ratio, the gramoxone is added with water and stirred; the 
MCPA-Na is added with water and stirred; the two are mixed and stirred, the 2-Amino-6-methyl-4-propyl-1, 2, 4triazolo [1,5a] pyriin-5(4H)-on is added into the well mixed and stirred gramoxone and MCPA-Na and stirred; the penetrant and synergist and the mixture are all added into a kettle to be stirred for 10-15 minutes; water is added and stirring is carried out for 20-30 minutes; and then standing, filtering, filling and sampling analysis are carried out, thus finished product is obtained. The invention overcomes the defect of the existing 
weed killer that single 
weed can be killed, is a quick-acting touch out type broad-spectrum 
weed killer, has fast action on broadleaf weed in gardens of rice, wheat, barley, corn, peanut, potato, cotton and mulberry and is safe to crops, dosage is 200-300g per mu, and application cost is 11.9-9.75% (mu / once) lower than that of other similar products.