The invention discloses a method for improving the water-fertilizer utilization efficiency and soil quality of a tobacco field of a southwest tobacco area. The method comprises the steps that before flue-cured tobacco transplantation, soil of a ploughing layer is subjected to deep ploughing, turning and flatting; in the same land parcel, in the pre-set fixed direction, concave shallow flat ditcheswith the width of 80-100 centimeters and the depth reaching the bottom of the ploughing layer are dug, the distance between the center lines of every two concave shallow flat ditches is 120 centimeters, and the distance between the adjacent edges of every two concave shallow flat ditches is 20-40 centimeters; thin short crop straw is laid at the bottoms of the concave shallow flat ditches, the laying thickness is 5-10 centimeters, and soil mixing is avoided in the laying process; the soil dug out during digging of the concave shallow flat ditches covers the laid thin short crop straw to formridges; flue-cured tobacco is planted on the ridges; after the flue-cured tobacco is harvested, the ridges are raked flat, and the rotten thin short crop straw at the bottoms of the ridges is sufficiently and evenly mixed with the soil of the ploughing layer. By applying the method, the water-fertilizer utilization efficiency of the tobacco field can be improved, and the soil of the southwest tobacco area is improved.