The invention discloses a steel arch and mesh mounting mechanical arm of a tunnel heading machine, which is applied to the field of tunnel heading machines. The steel arch and mesh mounting mechanical arm of the tunnel heading machine comprises a main frame, a rotation ring, hydraulic motors, a main beam, travelling wheels and transition oil cylinders. The main frame is connected with the travelling wheel in a matched mode, and the travelling wheels are mounted on the main beam; one end of every transition oil cylinder is connected with the main frame, and the other end of the transition oil cylinder is fixed to the main beam; the fixing ring and the main frame are welded together; the hydraulic motors are mounted on the fixing ring and connected with pinions; a winding disc is fixed onto the main frame; protection wheels are arranged inside the fixing ring; the rotation ring is sleeved outside the fixing ring; one end of every support oil cylinder is hinged to the rotation ring, the other end of the support oil cylinder is connected with an arch support arm or a grabbing support arm or a mesh support arm; every grabbing support arm is connected with a grabbing head, and every mesh support arm is connected with a mesh picking rack. The steel arch and mesh mounting mechanical arm of the tunnel heading machine is simple in structure, convenient to operate and high in efficiency and perfectly integrates the functions of steel arch installation and steel bar mesh installation.