The invention discloses an under-actuated walking robot. The under-actuated walking robot comprises a main body (1), a walking unit and a driving mechanism which is installed inside the main body (1) and used for driving the walking unit. The under-actuated walking robot is characterized in that the driving mechanism comprises a first drive shaft (2.1) and a second drive shaft (3.1), wherein the first drive shaft (2.1) is sleeved with the second drive shaft (3.1). The walking unit comprises a first drive rod (2.2), a first driven rod (2.3), a second drive rod (3.2) and a second driven rod (3.3), the first drive rod (2.2) and the first driven rod (2.3) are connected in a rotating mode through a connecting shaft (4) with the self-locking function, and the second drive rod (3.2) and the second driven rod (3.3) are connected in a rotating mode through a connecting shaft (4) with the self-locking function. By means of the structure, the robot can simulate the two feet of a human body to walk forward alternately, the structure of a movable unit is relatively simple, meanwhile, the number of driving units is small, and cost is low.