Time-frequency analysis theory was used in this work to analyze chirped optical pulse signals produced in directly modulated semiconductor lasers or optical propagation channel. The partial characters of the chirped signals can be depicted at time domain and frequency domain simultaneously using these methods. For chirped gaussian pulse signals which are commonly used in optical communication, Short Time Fourier Transform and Wavelet Transform as the examples of linear time frequency transform and Wigner-Ville
distribution as for nonlinear time-frequency transform are analytically presented. In the end, both advantages and disadvantages of the time-frequency analysis methods are compared.