Five classrooms in a Primary School in Xuanwu District of Beijing were chosen for investigation of indoor air quality. In the autumn measurement period and in the winter measurement period, various dust particle fractions (PM10 and PM2.5) were monitored indoors and outdoors continuously by portable monitors and samplers. Applying statistical software, the impact of different parameters on particulate matter (PM10 and PM2.5) mass concentration was then quantitatively analyzed. The main conclusions were included as follows: (1) Exposure to PM10 and PM2.5 in the indoor air of classrooms in autumn and in winter was high, especially that of PM2.5 in autumn. (2) The indoor PM10 and PM2.5 mass concentrations were related to different parameters including relative humidity, temperature, carbon dioxide, area of opened windows or louver windows, number of students and room volume/student and so on. (3) No marked differences in indoor PM10 and PM2.5 mass concentrations were observed between autumn and winter (p>0.05). However, a statistically significant influence of class level on the indoor PM10 and PM2.5 mass concentrations was apparent in both measurement periods (p<0.05).