In order to achieve higher adaptability, the control strategy based on walking sequence adjustment for accommodating unexpected slope terrains in bipedal walking is proposed in this paper, which consists of the Zero-Moment-Point (ZMP) tracking control, foot landing control, posture &yaw control. In our previous work, the 3-D walking sequences (WS) were defined and the online walking pattern generation based on the modified minimal orbit energy control (MMOEC) was realized. In this paper, utilizing the sensory reflex, the walking status is estimated and walking modes are judged when walking on slope terrains. Then, considering the stability and feasibility constraints, the real-time WS adjustment strategies for different walking modes are proposed. For the stabilization control, combining the modified preview control with the MMOEC by the angle coefficient, the ZMP generation and tracking control is first realized. Besides, the foot landing control is also adopted to reduce the impact force and accommodate the unknown terrain. With the posture control and yaw reduction, the stable biped walking on slopes terrains are realized, without a priori information.