The research and development of small-invasive sampling machine (SISM), which can be used to take out small dimensional samples from in-service equipment and to provide experimental materials for hydraulic bulging test and small punch test, has important application value in Engineering practice. This paper proposed a SISM and its design considerations. The sampling trajectory plan and small dimensional sample arrangement for improving sampling material utilization have been described. A unique semispherical machine tool was designed and the preparation method and performance characterization of the tool blade coating was studied. The tool rotary cutting motion and rotary feed motion were planned. A swing-level-type centering mechanism was designed as feeding mechanism. Samples of form of spherical crown with diameter 35mm and thickness 4mm can be take down from in-service equipment.