Disclosed in the present invention is a post insulator, comprising a hollow insulating tube, a shed positioned on periphery of the hollow insulating tube, and an upper flange and a lower flange provided at two ends of the hollow insulating tube, wherein gas is sealed inside of the hollow insulating tube, and the absolute pressure of the gas is 0.1-0.15 MPa. Further disclosed is an insulated support post formed by the end-to-end connection of the post insulators. The post insulator and the insulated support post of the present invention solve an interface problem present in internal insulating solid material filling, and also solve a gas leaking problem that occurs when using high-pressure gas filling, such that the post insulator does not need to be detected and maintained. At the same time, the margin of the micro-water control range is improved, and micro-water control and production difficulty is reduced.