An improved MDO procedure for BLISS 2000 (Bi-Level Integrated System Synthesis 2000), which is named HBLISS (Hybrid BLISS) to find a way out of a difficulty in applications because of the weighting factor, is proposed. The basic algorithm structure of BLISS 2000 was kept and the weighting factor was cancelled, in which the minimum residual error of coupled variables was utilized to coordinate system level optimization and sub-system level optimization. The algorithm structure and flowchart were introduced. The results of Reducer optimization problem show that HBLISS has the superiority in the disciplinary autonomy and convergence, and the improvement is valid.