This paper discussed the result of soft ground improvement of an expressway located in Pearl River delta and its foundation was treated by preloading combined with packed drain of a diameter of 7 cm. Testing and monitoring results showed that the adopted method of ground treatment was very effective, so the preloading time when degree of consolidation reach 80% was reduced by 1/3 as compared with the design anticipation. Moreover, appropriate decrease of packed drain spacing was useful to the pore pressure dissipation and soil consolidation. Packed drains also have a vertical reinforcement and anti slide effect besides the drainage. Soil shear strength has a significant decrease due to disturbance after construction of the packed drains, which should be seriously considered for practice technicians and academic authorities.