In order to further improve the tunable range of the tunable optoelectronic oscillator based on Mach-Zehnder interferometer(MZI), the influence of the relative power ratio of the two arms and the arm length difference of the two arms in the MZI on the transmission performance of the optoelectronic oscillator is discussed and analyzed. Through simulation analysis, it can be known that when the relative power ratio of the two arms of the MZI is 0.5, when the arms length difference changes between 12 mm~50 cm, the optoelectronic oscillator can output a single frequency microwave signal in the range of 0.411~16.892 GHz.