Objective To compare the pharmacokinetics of moxifloxacin (MXF) administered orally in the plasma and lung tissues of rats with pneumonia infected by Streptococcus pneumoniae (S.p) and normal rats. Methods To establish a model of Streptococcus pneumoniae pneumonia rats and normal rats. Moxifloxacin was administered by intragastric administration at 42 mg/kg. Microdialysis technique was used to sample the blood and lung tissues of pneumonia rats and normal rats to determine the free drug concentration of moxifloxacin in each sample, calculate the pharmacokinetic parameters, and compare the pharmacokinetics of oral moxifloxacin in pneumonia rats and normal rats. Results The t_1/2 of moxifloxacin in the blood of normal rats and pneumonia rats were (5.27±4.38) h, (2.15±0.07) h (P>0.05), and C_max were (4.94±0.98) μg/ml, respectively, (4.83±0.05) μg/ml (P>0.05), C_{last_obs}/C_max were 0.02±0.03, 0.27±0.04 (P<0.05), AUC_0-t were (22.33±2.02)μg/ml·h, (12.88±1.19)μg /ml·h (P<0.05), CL/F are (1.79±0.11)(mg/kg)/(μg/ml)·h, (2.49±0.26)(mg/kg)/(μg/ml)·h (P<0.05); C_max of lung tissue of normal rats and pneumonia rats were (1.42±0.05) μg/ml, (4.84±0.02) μg/ml (P<0.05), t_1/2 are (1.9±0.63)h, (3.39±0.79)h (P>0.05), AUMC are (11.93±5.14)μg/ml·h², (107.01±25.39)μg/ml·h² (P<0.05), AUC_0-t are (3.06±1.0) 7μg/ml·h, (13.16±0.53)μg/ml·h (P<0.01). Conclusions ① Under the 400 mg/d dose condition, after intragastric administration of moxifloxacin, the concentration of free drugs in the blood and lung tissues is higher, far exceeding the minimum inhibitory concentration (MIC) and anti-drug resistance concentration (MPC), can effectively remove Streptococcus pneumoniae. ②The free concentration of moxifloxacin in the lung tissue of rats infected with Streptococcus pneumoniae is always higher than that of normal rats, and the C_max is about 3.4 times that of normal rats. The penetration rate of moxifloxacin in lung tissue of pneumonia rats is significantly higher than that of normal rats.