Light chirp is a major issue in optical fiber links. This letter deals with precise characterizations of the frequency chirp parameters of reflective semiconductor optical amplifiers (RSOAs). The RSOA chirp properties are represented by transient and adiabatic chirps, whose parameters are characterized utilizing a ratio between the phase and the amplitude modulation depths of the RSOA when modulated with sine waves. Utilizing a high-resolution optical spectrum analyzer, a RSOA linewidth enhancement factor \alpha and an adiabatic factork are obtained experimentally, based on which the influence of chirp parameters on the transmission performance of non-return-to-zero (NRZ) signals can be analyzed.