In industrial production, precise control of liquid levels within containers holds paramount importance in ensuring smooth equipment operation and safeguarding the lives of maintenance personnel during production and transportation. This paper proposes the utilization of a laser swept frequency interferometry measurement system for liquid level assessment, which has many advantages, such as large measurement range, non-contact measurement, swift response time and convenient operation. Given that liquids exhibit a relatively high absorption rate for infrared light; the backscattered signal acquired by the measurement system is exceedingly weak, leading to a less-than-ideal signal-to-noise ratio. To address this issue, the phase accumulation method is introduced and combined with the measurement system to improve the accuracy of liquid level detection. In each cycle of the signal, the effective information carried by the signal remains consistent, and the noise information is then random. Therefore, employing the phase accumulation method not only amplifies signal strength but also elevates the signal-to-noise ratio. Further, by utilizing a phase-frequency sampling technique for nonlinear correction of the signal, followed by data processing, the liquid level information can be obtained. The experimental results show that the phase parameter accumulation method has a significant effect on increasing the signal strength and signal-to-noise ratio, thus providing a promising approach to enhance measurement precision under conditions of low signal-to-noise ratio.