The invention discloses a method for detecting a rotational wave packet of a molecule, which comprises the following steps: exciting a molecule by using two beams of pumping light having a fixed timedelay to obtain a unidirectional rotational molecular beam; using a beam of probe light to act on the rotational molecular beam, and producing higher harmonics containing molecular rotational wave packet information; collecting a higher harmonic spectrum under different time delays and different polarization angles of the probe light and the pumping light; and deconvolving the higher harmonic spectrum to obtain rotational wave packet of the molecule. The method for detecting a rotational wave packet of a molecule in the invention proposes a method for acquiring the molecular rotational wave packet information by detecting the higher harmonics, which is a simple and effective method with broad applicability for simultaneously detecting an electronic dynamics process of an attosecond time scale and a nuclear dynamic process of a femtosecond time scale.