The invention discloses a trunk-supported walking aid lower limb power orthosis. The orthosis comprises a shoulder supporting assembly, a walking aid assembly a waist supporting assembly and a lower limb power orthosis assembly, and the lower limb power orthosis assembly is used for supporting the trunk of a human body to be upright and adjusting abnormal postures in the walking process; according to the shoulder supporting assembly, the width symmetric adjustment design of the shoulder and back portion is achieved through a connecting rod structure; and according to the walking aid assembly and the rear-mounted walking aid, support can be provided when a patient wears the device to move, other supporting tools such as a walking stick are not needed, the trunk can be made to be more upright, and constraint of other supporting tools is reduced. According to the invention, three-degree-of-freedom adjustment of the hip joint, one-degree-of-freedom adjustment of the knee joint and passive assistance of the ankle joint in the walking process are realized; according to the invention, change angles of joints of lower limbs of normal gaits of a human body can be adapted; the size can be adjusted to adapt to people with different figures, and the comfort level of the equipment is improved; and the modularized design can be detached and replaced at any time, different requirements are met, and cost is saved.