This paper introduces a kind of composite plunger pump with small volume, stable operation, high efficiency and compact structure. This pump is used for uterus thermal ball therapy instrument removing endometrium to solve the problem of needing pneumatic positive pressure drive and pneumatic negative pressure drive for the treatment gun simultaneously. It can also be used to figure out the problem of structure complexity, installation and maintenance inconvenience and poor stability of  the drive system  resulting from pneumatic and vacuum circuits. Moreover, the composite plunger pump can also provide power for other instruments and equipment that need both positive and negative pneumatic hybrid power.