Abstract: Seismicity fuzzy entropy H is defined in this paper. That seismicity fuzzy entropy values change with time, with space before Tangshan earthquake is computed in this paper. It is discovered that seis micity fuzzy entropy values fell down be fore Tangshan earthquake, and Tangshan earthquake occurred at the area of low seismicity fuzzy entropy value. This result fits well with the law that seismicity in earthquake source area changes from disorder to order before large earthquake. Seismicity fuzzy entropy unifys the fuzzy factor and the seismicity entropy as one, it can reflect seismicity anomaly better than seismicity entropy itself.