In order to evaluate the effective detection distance of bio-aerosols and sensitivity to the concentration of the bio-aerosols for the laser induced bio-aerosols fluorescence lidar. On the basis of elaborating lidar measuring principle, a fluorescence lidar employing a Nd: YAG laser at 355 nm as a transmitter is designed for biological aerosol concentration detection. The signal-to-noise ratio (SNR) of bio-aerosols fluorescence echo signal is simulated based on the main parameters, such as pulse energy, pulse number, filter bandwidth, diameter of telescope, field of view of telescope and inelastic scattering cross-section of bio-aerosols particles. With the uncertainty of less than 10%, theoretical analysis results show that the system is capable of measuring bio-aerosols with a mass fraction of 10-12 up to an effective detection distance of 1.0 km and 7.8 km at daytime and nighttime, respectively. Moreover, with a certain detection rang of 0.5 km, the fluorescence lidar is able to detect bio-aerosols at a minimum mass fraction of 1.8×10-13 at daytime and 1.0×10-14 at nighttime. Simulated results are helpful to understand the optimal parameters of laser induced fluorescence lidar and also the best experimental environment of the system, and then realize effective detect to bio-aerosols.