Based on the daily maximum temperature data and hospital Emergency Room (ER) visit records from 2009 to 2012, we analyzed the climatic impact on the onset of the four types of common respiratory diseases (i.e., upper respiratory tract infection, bronchitis, pneumonia, and asthma) in Beijing, China. We used a time-series-based semi-parametric generalized additive model. We controlled the confounding factors, such as weekday effect, long-term trend, and other meteorological elements, and we also factored in age-gender differences and the lagging effect within a week. The results showed that the lagging effect of daily maximum temperature on the number of ER visits due to respiratory diseases was within one day. The number of male patients was generally higher than that of female patients. For each 1℃ increase in daily maximum temperature, the number of ER visits due to upper respiratory tract infection and bronchitis would increase by 2.10% and 2.14%, respectively, for the male subgroup; and the number of ER visits due to pneumonia, asthma, and bronchitis would increase by 2.00%, 4.21%, and 2.95%, respectively, for the female subgroup. Within the four different age subgroups, the increase in the number of ER visits due to respiratory diseases per 1℃ increase in daily maximum temperature was statistically significant with the exception of the 60-74age group. In particular, when daily maximum temperature increased by 1℃, the number of ER visits due to bronchitis would increase by 3.60% and 2.16% for the below-15 and the 15~59age group, respectively; the number of ER visits due to pneumonia and asthma would increase by 2.69% and 8.05%, respectively, for the over-75age group.