Abstract: Objective To quantitatively assess the impact of ambient PM10 on hospital outpatient visits for respiratory diseases. Methods Daily hospital outpatient visit data in 2012 were collected from two hospitals in Shenzhen. Daily meteorological and air pollution data in the same duration were obtained from Shenzhen Meteorological Bureau and Shenzhen Environmental Protection Bureau, respectively. A time-series analysis using a generalized additive model (GAM) was applied to assess the association between ambient PM10 concentration and hospital outpatient visits for respiratory diseases after adjustment for long-term trend, day-of-week, meteorological factors and other air pollutants.Result The average PM10 concentration in Shenzhen in 2012 was 0.052 mg/m3, meeting the national second-level standard. The total outpatient visits of the two involved hospitals were 562 174 with an average of 1 535.99 persons per day. GAM models indicated a positive association between ambient PM10 concentration and hospital outpatient visits for respiratory diseases. In the single-pollutant models, the effect of PM10 was largest on lag 6 days（RR=1.004 7, 95%CI:1.003 6～1.005 8）. In multi-pollutant models adjustment for CO, O3, NO2 and SO2, the RRs for the increment of PM10 concentration varied, and the RRs in the models adjustment for SO2 (RR=1.005 9) and models adjustment for CO and SO2 (RR=1.006 7) were the largest two. Conclusion The ambient PM10 concentration was positively associated with hospital outpatient visits for respiratory diseases in Shenzhen, and a lag structure was found in these associations.