Abstract：It is of great scientific significance to study the spatial and temporal changes of 400 mm precipitation contour in order to deal with the impact of global change on regional ecological environment and social economy. For annual precipitation observations recording from 752 sites in China from 1951 to 2012 year,the annual precipitation distribution in China mainland during 62 years is obtained by inverse distance weighting interpolation method,and the weighting average method is used to obtain the 400 mm precipitation contour during 62 years. The conclusions are as follows:( 1) the annual average rainfall of China from 1951 to 2012 shows a downward trend,and the annual decline rate is 6. 77 mm / a;( 2) from 1951 to 2012 year,China 400 mm precipitation contour overall weighting average position is 105°56' E,37 °51' N,it has a moving tendency to east and north,overall eastward 6°42',overall northward 2°26';( 3) the 400 mm precipitation contour has distinct characteristics of segmentation. The eastern part is appeared after 1975,since then 37 years the 400 mm precipitation contour move to the east nearly 1 850 km.

Keyword：400 mm precipitation contour;segmentation feature;the inverse distance weighting method;the weighted average of the position;