From the tuning mechanism of the DFB laser diode, we establish an analytical model for current and temperature tuning characteristics. The parameters of the model are identified by experimental results. The model is used to analyze the four DFB diode lasers, and the transient characteristics of the lasers are obtained. We also obtain the static characteristics of these lasers from Agilent 86142B Spectrometer. The comparison between the two values indicates that the correlation coefficients are both more than 0.9999. At the same time, according to the absorption spectrum of CO2 gas, we also measure the emission wavelength of lasers. Comparing it with the HITRAN spectrum of CO2 absorption lines, the two errors are shown to be within 3pm. The analytical model can accurately predict the transient output wavelength of lasers in tuning, the accuracy can meet the spectrum, optical coherence measurements and other practical requirements.