Pollen is an important part of bioaerosols, and its complex refractive index is a crucial parameter for study on optical characteristics and detection, identification of bioaer- osols. The reflection spectra of pear pollen within the 2.5~15μm waveband were measured by squash method. Based on the measured data, the complex refractive index of pear pollen within the waveband of 2.5 to 15 μm was calculated by using Kramers-Kroning (K-K) rela- tion, and calculation deviation about incident angle and different reflectivities at high and low frequencies were analyzed. The results indicate that18 degrees angle of incidence and different reflectivities at high and low frequencies have little effect on the results, and it is practicable to calculate the complex refractive index of pollen based on its reflection spectral data. The data of complex refractive index of pollen have some reference value for optical characteristics of pollen, detection and identification of bioaerosols.