This paper is investigated feasibility of using Bragg Grating sensor to determine salinity and temperature. To achieve this purpose, a fiber Bragg grating (FBG) was used in the laboratory environment as well as water with different temperatures and salinities. Generally, the FBG is a type of optical reflector made in core of optical fiber. The mechanism of this grating is that it reflects a certain wavelength of light by passing an alternating change in the refractive index of the fiber core and passes the rest of the wavelength. The results show that FBG sensors are very sensitive to temperature, salinity, pressure variations and are the suitable devices for measuring these environmental parameters. Based on these facts, we try to create a correlation between changes in temperature, salinity and shift of length waves. The outputs indicate that wavelength sensitivity are 0.0104 nm/⁰C and 0.0533 pm/mg temperature and salinity respectively. In addition to this, some limited cases are used to estimate sensitivity of this sensor to evaluate instability in water column.