Abstract: In this paper, staistical analyses of isoseisms of historic earthquakes have been done.It is pointed out that the distance distribution of influencing intensity I that is greater than a specified value under condition of given epicentral intensity I₀ basically follows log-normal distribution whose expectation value μ(I₀,I) and standard variance σ(I₀,I) are determined as shown in Table 2.In order to relate the statistical results with the cirrently used formula of average intensity atteauation I=C₁+C₂I₀-C₃ln(R+R₀), the regres sion analysis of μ(I₀,I)'s obtained by this study are also done. As results, the coefficients of the regression expresion have been obtained and listed in Table 3. The results shown in this paper can be used in seismic risk analysis and inensity zoning.