Abstract: Based on continuous drainage boundary conditions, the one-dimensional consolidation equation considering self-weight is established. Using the Finite Sine Fourier transform method, the analytical solution is proposed, and the undrained symmetric plane is presented by the numerical method. The influence of the interface parameter and gravity coefficient on the undrained symmetric plane is discussed. Aiming at the optimization problem of horizontal drain in engineering practice, the consolidation equation considering self-weight is established, and the optimal position of the sand blanket under different time factors is proposed by the semi-analytic method. The influence of the sand blanket position on the consolidation degree is investigated, and the relationship chart of the position and time of the optimum sand blanket under different soil interface parameters is further given. The results show that the undrained plane considering self-weight varies with time. The larger the weight coefficient is, the closer to the bottom soil is the undrained plane of symmetry. The optimal placement of sand blanket also varies with time. An engineering example is provided to show that the optimization of drainage sand blanket has obvious effect on the improvement of consolidation time efficiency.