In numerous propulsion forms of underwater creatures, jet propulsion is one of the major ways to swim, and so far, the main bionic objective of current jet-propelled bionic robots are cephalopods (such as octopuses and squids). However, scallop has unique advantages to survive underwater for its structure and jet propulsion style. In this paper, a scallop robot that mimics the structure and the propulsion mechanism of a scallop is designed and implemented. The scallop robot consists of two shells, a special motor to drive the shells open and close periodically, and a curtain muscle to control the water flow during swimming. The scallop robot absorbs water from the front in the direction of movement, and then sprays water to the rear, with better continuity of movement and endurance compared to other jet propulsion forms. Moreover, the rigid shell protects the carrying device well. Swimming experiments show that the scallop robot's special jet propulsion mode enables it move up to 1.8 body length/second. The developed scallop robot has many potential applications for its good swimming continuity, stable swimming, strong protection, and low-cost structure.