The paper proposes generation methods for humanoid robot walking using a central pattern generator (CPG) based joint modification method to improve the adaptation ability on various slop terrains. Although CPG has basic adaptation ability for the different terrains, but it might be limited to small variations of those. In order to increase terrain adaptability we supplement the modification of joints using genetic algorithm on the output signals of the CPG oscillators. We have tested the two methods to investigate an adaptation capabilities of humanoid walking on various slope terrains with different slope angles using the humanoid robot Nao in the Webot simulation. The performances of humanoid walking on various slope terrains are analyzed.