In this paper, we present the design, fabrication, and performance test of a gap adjustable molten metal drop-on-demand (DoD) inkjet system with a cone-shaped piston head, which can eject a droplet of lead-free molten solder at high temperature. The gap adjustable mechanism with the cone-shaped piston head is proposed for optimizing the gap distance between the chamber wall and piston head. The droplet diameter and velocity can be controlled in a wide range by moving the initial gap distance and minutely by controlling the chamber pressure. Stability and satellite can be partly adjusted by controlling the initial gap distance and the chamber pressure, respectively. The working temperature is improved by locating the piezoelectric actuator at the outside of the furnace and by inserting the insulation block between the print head and the actuator. From a practical point of view, the molten metal DoD inkjet system presents a simple structure for easily interchangeable nozzle parts, even though the nozzle is choked. The gap adjustable molten metal DoD inkjet system with cone-shaped piston head has great potential as a manufacturing tool for direct printing a viscous material at various temperatures. It is expected to be applicable in many industrial fields including semiconductor packaging, electrode bonding, printed electronics, information, and display industry.