Abstract: Analyzed are the advantages and shortcomings of the three typical leak testing processes for the stainless steel tube and the titanium alloy tube,i.e.,underwater pneumatic test,hydrostatic test and eddy-current or ultrasonic nondestructive test.Described are the work principle,operation procedure,evaluation criteria and advantages of the new pneumatic leak testing process.The analysis leads to such a conclusion that among the commonly-used leak testing processes for the stainless steel tube and the titanium alloy tube,the said new pneumatic process is distinguished from the others with such advantageous features as high sensitivity,full automation,and above all,employment of hi-sensitive pressure or differential pressure sensor,and using reference pipe with 0.076~0.152 mm fine leakage holes as made by means of the laser-punching method.