The characteristics of interdecadal variation of highrisk forestfire periods in spring in Heilongjiang Province are analyzed by using the observation data from 29 stations of Heilongjiang Province from 1961 to 2006．The results indicate that the highrisk forestfire periods in spring in the western and southern parts of Heilongjiang Province are longer than those in the eastern and northern parts. The highrisk forestfire periods in spring have obvious interdecadal variability with the most rapid lengthening in the 1990s, but there are some differences among various areas, with the lengthening in the southwestern and eastern of Heilongjiang Province beginning from the 1970s．Moreover，the climatic background of interdecadal variability of the highrisk forestfire periods is also discussed preliminarily. The interdecada1 variation of highrisk forestfire periods in Heilongjiang Province from the 1990s may be related to the global climate warming and the interdecadal variation of atmospheric circulation systems.