The estimated quantity of rice straw and its use in some provinces in Mekong Delta were carried out based on interview and field survey in An Giang, Dong Thap, Kien Giang and Can Tho. The results showed that there was six common methods that used by farmers for rice straw treatment. They are burning, burying, mushroom cultivation, breeding, sale and giving to other farmers. The methods of using rice straw was vary depend on the rice seasons. In winter-spring season, straw burning is the most common method that used by farmers (98,2%), whereas the opposite was true for mushroom cultivation, sale. In the summer-autumn season, the proportion of straw burning decreased to 89,67% level, burying accounts for 6,65%. In autumn-winter season, burning had lowest level (54,1%), the proportion of straw burying was quite high (26,1%), followed by mushroom cultivate (8,14%) and the rest shared the small proportion. The estimated quantity of rice straw in the Mekong Delta in 2011 was approximate 26.2 million tons annually, in which 20.9 million tons was burn directly on fields. This lead to release to the asmostphere about 17.9 million tons of CO₂, 485.68 thousand tons of CO and 10.48 thousand tons of NO_x. The results also showed that most of farmers tend to continue using burning as the most popular method in the next few years.