Abstract: The changes of pore water pressure in the core wall of earth - rockfill dam are generally delayed relating to that of the reservoir level. Based on statistic analysis of the pore water pressure in core wall of Lubuge dam, a new method is proposed, that is, to take the average rate of the rise and fall of reservoir level and its water head with the maximum degree of correlation as the variables, and then make statistic analysis of pore water pressure for measuring points, as a result, the coefficient of multiple correlation and standard deviation are improved significantly.