Abstract: This article develops a stereoscopic photogrammetric tidal level measurement technique which does not require sea surface control points. Firstly, this technology determines an equipotential surface P and gravity direction near the true average sea surface through a sequence of images collected in a short period of time, and then uses stereo photography wave measurement technology to measure the sea surface displacement changes caused by waves to further determine the relationship between the average sea surface and equipotential surface, thereby achieves water level elevation measurement. The article presents the geometric model of stereoscopic photography tidal level measurement, as well as the control equations and specific algorithms for each link of the model. A lasting 26 days technical validation experiment was conducted based on the Bohai oil platform. Through a set of experimental image sequences, the calculation methods and results of important aspects of the geometric model were elaborated, verified, and demonstrated in detail. Offshore experiments have shown that, compared to traditional water level gauge measurements, 50% of measurement points have measurement errors within 2 cm, 73.6% of them have measurement errors within 4 cm, 88.8% of them have measurement errors within 6cm, and only 4.5% of them have measurement differences greater than 8 cm, fully demonstrating the accuracy and feasibility of this technology. This technology does not require calibration of sea surface control points, which is easy to operate, economical, and not easily damaged by fishing activities, to some extent, compensates the shortcomings of tidal level monitoring equipment.