Aimed to the large dispersion situation of the rocket booster or sub-stage falling to the ground without controlling, the line target homing method of parafoil system was put forward. The calculation model of rectangular boundary was established, and the contraction regional analysis of two kinds of homing methods namely point target and target line was performed. The influence of parafoil homing ability and the scattered boundary characteristics of falling area on homing performance were analyzed, and the corresponding homing strategy was obtained. A solution for setting up multiple landing areas in larger dispersion area was proposed. Finally, the dynamics and control model was established and the line target homing process was simulated. Satisfactory results are obtained，which shows that the proposed method has some reference value to the project.