Objective To explore a method for earlier evaluating death toll based on a function relationship ( an increasing hour-increasing death index ( K value) followed with time (T) changing after catastrophic earthquake. Methods Information data of 10 typical occurrences of catastrophic earthquake obtained from China International Search and Rescue Team (CISAR) were analyzed. Total deaths were estimated according to the simulation function made by hour-increasing death index (K value) followed with time (T) changing. Expected value of the simulation function was assessed by statistical software SPSS version 17.0 to establish the model of simulation function.Results The length of time (T) to reach K maximum (Kmmax) was ( 12.94 ± 8.18) h and then the K value was gradually decreased. Kmax was symmetrically scattered within 2 T time.Estimated death toll (W) within 2 T was obtained from calculating the integration summation of the function to get a formula as W =∫∞ kf(t) dt.This Estimated death toll(W) numbers was correlated approximately with the death toll (M) from authoritative report (P ＜ 0.01 ).According to the regression analysis of model simulation curve,the predictive function of death toll within 2 T was M =W1.23 ×0.194.A determinant coefficient of this power function R2 was 0.88. Conclusions Earlier estimating death toll within about 12 h should be carried out by using the data of real-time information report system.