The definition, status and development of frictionless air cylinder are presented. As design guidance, leakage model of long piston cylinder during starting action stage is built. It shows influences of clearance, length of piston and other parameters on seal ability. Leakage model of another piston with two rows of small pores is introduced and studied. In those structures the number and diameter of holes as well as clearance of piston-cylinder are key factors of leakage. Based on above models and principles, a new type of air bearing piston with pores, pressure distribution groove and seal gaps is proposed and a single-acting frictionless cylinder is designed. Its pneumatic experiments have been done in a set of test system. Test results show this cylinder’s friction is near 0 and it behaves reliable performance under stable pneumatic resource.