The invention discloses a multi-cylinder hot-air engine. The multi-cylinder hot-air engine comprises a machine body and a power cavity formed in the machine body. Four air cylinders which are distributed at equal intervals from left to right are arranged in the inner wall of the top of the power cavity in a communicating mode. Exhaust switch cavities are formed in tops of the air cylinders in a communicating mode. Air inlet switch cavities located at the right ends of the exhaust switch cavities are formed in the inner walls of the tops of the air cylinders in a communicating mode. Pistons areslidably connected into the air cylinders in a matched mode. The bottoms of the pistons are connected with first connecting rods extending up and down in a hinge joint mode. The tail ends of the bottoms of the first connecting rods stretch into the power cavity. Output shafts which extend left and right are rotatably connected into the power cavity in a matched mode, and the output shafts are provided with crank shafts located at the bottoms of the air cylinders. One power connecting mechanism is arranged between every two crank shafts.