Based on the measured hourly precipitations at 38 meteorological stations in Xizang from 1981 to 2020, the spatio-temporal characteristics of daytime precipitation (Pd) and nighttime precipitation (Pn) and night-precipitation rate (Nr) in recent 40 years are analyzed by the methods of linear trend estimation, Pearson coefficient and Mann-Kendall test. The results show that, in Xizang the multi-year average of annual Pd decreases from east to west, the annual Pn decreases from southeast to northwest, and Pn is larger than Pd. The middle reaches of the Yarlung Zangbo River are the center Nr in Xizang. The correlations between the Pd and Pn and the altitude are most significant in spring, and the correlation coefficients between the Pd and Pn and the longitude are the greatest in summer, autumn and the whole year. In winter, Nr at high latitudes is larger than that at low latitudes. In summer and autumn, Nr at high altitudes is smaller than that at low altitudes. In the past 40 years, the annual Pd and Pn increased at 73.7% of stations in Xizang, while the annual Nr showed a decreasing trend at 57.9% of stations, of which the variation trend of Pn was more obvious than that of Pd at 63.2% of stations. The average annual Pd and Pn increased in Xizang, mainly in spring and summer, and the growth rate of annual Pn was greater than that of Pd. Due to the decreased Nr in winter, spring and autumn, the annual Nr tended to decrease. On the interdecadal scale, the Pd and Pn in the 1980s were the least in Xizang in the past 40 years, with the maxima of annual Pd and Pn appearing in 2010s and in 1990s, respectively. For Nr, the maximum and minimum occurred in the 1980s and in the 2010s, respectively. According to the Mann-Kendall test mutation test, the abrupt changes of climate for the Pd and Pn in spring and Pn in winter occurred in the late 1990s and at the beginning of 21st century, respectively, with the former increasing and the latter decreasing. The years 2004, 2011, and 2009 were the time of mutation for winter, spring, and annual Nr, respectively.