We experimentally and theoretically study the alignment structures of the rotational wavepacket created by linear molecules and two strong femtosecond laser pulses. In the experiment, we observe that the alignment structures depend on the time delay between the two laser pulses. In the theory, we find that the alignment structures are composed of the self-coupling term and the cross-coupling term. The contributions of these two terms are separately calculated. Their coherent superposition reproduces the alignment structures observed in the experiment.