It is shown that the time-dependent intensity of an ultrashort laser pulse can be recovered from the secondorder correlation G(2) (τ) and the third-order correlation with single time-delay G(3) (τ) . A calculation method for recovering the intensity enveloped I(t) is presented. The experimental data are successfully processed by a computer with novel programming. A new instrument is suggested on the basis of determing I(t) of an ultrashort laser pulse from correlation measurements.