Lodging is one of the important factors that limits rice yield and reduces grain quality. Lodging obstructs the process of transporting carbohydrates from the leaves and stem to grains, and causes the panicles to sink into water and decompose, which causes many difficulties for harvesting. This study was conducted with the aimof determining the optimal paclobutrazol concentration with respect to the growth and hardness of rice to help limit lodging and increase the yield. The experiment was conducted in the field on the autumn-winter crop in Vi Thuy District, Hau Giang province. The experiment was carried out in a randomized complete block design (RCBD) with five paclobutrazol treatments (control (spraying water without paclobutrazol), 25 mg.l-1, 50 mg.l-1, 75 mg.l-1, 100 mg.l-1) and four replications per treatment. The results showed that the treatment of paclobutrazol at a concentration of 50 mg.l-1induced the rice to increase the number of tillers, the stems’ hardness index (the lodging index was reduced), the filled grain ratio, and the yield (6.98 tons/ha, increasing 12.1% compared to the control).