A method to determine chirp direction for ultrashort laser pulses is presented based on the asymmetry of interferometric autocorrelation(IAC) envelope,which is highly sensitive to the direction of chirp.The peak value of the difference modified by IAC envelope as a correspondence of chirp direction is found by analyzing the asymmetry of IAC envelope.Furthermore,measurement of direction of linear and quadratic chirp is obtained with the peak value and spectrum profile of ultrashort laser pulse.The theoretical analysis is supported by experiment.With this method,the linear and quadratic directions of chirp in ultrashort laser pulse are measured.