This paper presents the development and assessment of a liquid-level sensor using reflective long-period fiber grating (LPFG) technology. The LPFG was fabricated by the electrical arc discharge method and the liquid-level sensor consisted of five LPFGs in series with a reflective mirror (end) coated with silver by Tollen’s test. The experimental findings showed the sensor could be used to automatically monitor five liquid levels, such as 20, 40, 60, 80, and 100 cm. The sensing system had at least 100-cm liquid-level measurement capacity. The reflective LPFGs-in-series sensor was able to successfully yield a comparable liquid-level sensing performance and hopefully could be used in the fields of civil and agronomy engineering applications such as pipes, channels, dams, and deep-ponding paddy fields.