Brillouin frequency shift in a Brillouin scattering-based fully distributed fiber sensor is the combined effects of strain and temperature. A single Brillouin frequency shift can't achieve the information of strain and temperature, respectively, and the cross sensitivity limits the practice of the sensor. The present methods and working principles for solving the cross sensitivity are introduced. The relationship between Brillouin-scattering spectrum and strain or temperature of large effective area non-zero dispersion-shifted fiber (LEAF) is investigated. It is found that there are three Brillouin scattering peaks in the spectrum, which are linear with strain and temperature. The difference of Brillouin intensity between the first peak and the third peak is independent of temperature but is linear with strain. A resolution to solve the cross-sensitivity problem based on experimental results is given, and about 130 με strain and 8 ℃ temperature measurement resolution is achieved.