The utility model belongs to the technical field of substation application equipment and in particular relates to an online oil chromatography monitoring device capable of conveniently monitoring the carrier gas pressure. The device comprises an inflation bottle, a reducing valve and a pressure sensor, wherein an observation window is formed in a side wall of an enclosure shell; a bottle interior carrier gas pressure gauge and a carrier gas output pressure gauge are connected to the inflation bottle built in the enclosure shell; the bottle interior carrier gas pressure gauge is connected with the pressure sensor by virtue of a sensing line on the reducing valve; the pressure sensor and a carrier gas analysis module are arranged in a host; the reducing valve and the pressure sensor are connected to the host by virtue of a pressure sensing line; and the carrier gas analysis module is arranged in the host, and the data can be uploaded to the background. According to the device disclosed by the utility model, the carrier gas bottle pressure can be directly checked, the device abnormality or a device power failure phenomenon caused by error operations such as wrong touch of a device power supply because the chassis is opened by the field staff can be avoided, and the phenomenon that the device cannot normally operate because the carrier gas is used up is avoided.