The paper presents a novel method of wave group decomposition of ultrashort laser pulse propagating in second-order nonlinear dispersive medium We have derived the expressions of the decomposed wave groups under different conditions of SPM, GVD and chirp These results are fully discussed to have shown that thewave group decomposition method can give clear physical picture for pulse propagation in amplitude-maximum, time-delay and wave group frequency represntation It can also be employed in numerical simulation.