The invention relates to the technical field of semiconductors, and discloses a method for monitoring the thickness of a gate oxide layer in real time. After preparation of the gate oxide layer is finished and the physical thickness D1 is measured, a first native oxide layer thickness DOX1 and a second native oxide layer thickness DOX2 are defined; and the real-time thickness D=D1+DOX1+DOX2 of the gate oxide layer is monitored. The method comprehensively considers the waiting time Q-Time after preparation of the gate oxide layer and before a polysilicon gate deposition technology and the influence of the oxygen density O2-Density of a deposition region in the polysilicon gate deposition technology on the natural oxidation rate of the gate oxide layer, and achieves accurate monitoring on the actual thickness of the gate oxide layer. Compared with the prior art, the method can accurately monitor the real-time thickness of the gate oxide layer according to the technology progress, the technological conditions and the technology time. Compared with traditional actual measurement of the physical thickness of the gate oxide layer, the method is more detailed and accurate and avoids loss of monitoring significance since the monitored physical thickness does not conform to the final actual electrical thickness, so that the process quality is improved; and the device performance is ensured.