Precipitation in Heilongjiang Province of China increased slightly from 1960 to 2000. Adopting the method proposed by Arthur N. Samel, we separated monsoon rainband rain and calculated the initial and final date of monsoon rainband of each year and each station. For the period of 1960-2000, the change of annual precipitation in Heilongjiang Province, with an increasing trend of 2.229 mm per decade, is not significant; the duration and total monsoon rain decreased significantly, with a decreasing trend of -6.9 day per decade and -17.5 mm per decade separately. That change comes from early leaving date of summer monsoon rainband for the period of 1960-1975 and later arriving date of summer monsoon rainband for the period of 1990-2000. The weakening of summer monsoon makes its contribution to the annual precipitation decreased significantly, with a decreasing trend of 4.4% per decade.