We present a comparative assessment of several refractometric optical fiber platforms based on reflective long-period fiber gratings (RLPGs), which was fabricated by combining the long-period gratings with the different fiber optic reflectors such as fiber optic retroreflector, Faraday rotator mirror, and Sagnac fiber loop mirror. In the experiment the refractive index (RI) of liquid was measured with RLPGs. It was found that the reflection spectrum remained the resonant dip without interference in fringe and the resonant wavelength appeared obvious blue shift with the increase of external RI. The spectral depth was reduced about 20 dB after a fiber optic reflector was configured. The simulation result of the resonance wavelength change with the refractive index of the liquid was also given. Meanwhile, the sensitivity of surrounding temperature has been considered. During the temperature measurement process, the intensity hardly changed with temperature. The absolute error of LPG was 1.15dB, and the absolute error of RLPG was about 0.2. The refractometric optical fiber platforms with the configuration of RLPGs had several advantages such as longer sensing distance, RLPG operation mode and non-interference fringe. Combined with the advantages, the sensor structure can not only be applied to measure the RI of glycerol/water solutions, but also be widely used to the measurement of toxic chemical liquid based on the fiber characteristic of resistance to hostile environments, especially far away from the toxic source.