Precise estimation of precipitation in Taihang Mountains is crucial for understanding water cycle and providing support for water management in Haihe River Basin. By using Doppler radar, this study developed the Z-I relationships with different time windows (1-5 h) in three counties in eastern side of Taihang Mountains using radar reflectivity (Z) and rain gauge data (I) from June to September during 2013-2014. By dividing the 45 precipitation events into three categories: Light, moderate and heavy, precipitation was precisely estimated from different Z-I relationships under different categories. Take the rainfall event on 9 July 2013 as an example. It showed that (1) the errors of estimated precipitation from different time windows declined firstly, then rose up as the time windows moved from 1 h to 5 h, and the lowest error appeared in 2 h. (2) The 2 h Z-I relationship greatly improved the precision of moderate rain. (3) The estimation of heavy rain also improved when the 2 h Z-I relationship was applied to the rainfall event that happened on 9 July 2013.