Abstract: By logarithmic tran sformation of the analytic solutions expressing one-dimension water masstracer dispersion test with instant injection of tracer,a linea requation,whose independent variable X includes test data t and x,u with unknown value,dependent Y includes the test data c and t,and the linear constants include the long itudinal dispersion coefficient D,was derived.A ccording to the p inciple that the suitab levalue of u should make the value of correlation coefficient between Y and X extreme,the equation computing the value of u was derived.With known the value of u,the values of X correspond ingto different observation time may be computed.Then the linear constants may be determined by the method of linear regression to analyze the data of Y-X,and finally the dispersion parameters can be estimated.