The herein investigated blossoming flower automaton is one of the ingenious mechanical devices made in the 18th century to entertain people. Although this automaton is still preserved in the Palace Museum in Beijing, its inner works are generally not open by the public, and the mechanical structure is unknown. A reconstruction design procedure for ancient automata with unclear mechanical structure is provided, including mechanism design and performance analysis. One of the reconstructed mechanisms of the blossoming flower automaton is selected, and an easy-making cam with circular-arc profile is used. The motion characteristics are checked not only by computer-aid modeling and simulation but also through the prototype manufacturing and testing with 3D printing components and image/video analysis software, and the numerical results are presented for a performance evaluation and characterization.