We propose a new parameter, Qp,l2, based on cross-sectional intensity distribution to distinguish Laguerre–Gaussian (LG) beams. Theoretically, Qp,l2 shows an approximately linear dependence on the topological index in higher LG modes. Compared with the similar parameter Q_p,l proposed by Long et al. [Opt. Lett.38, 3047 (2013)] recently, our experimental result demonstrates that the approximate linearity of Qp,l2 brings out the advantage in characterizing higher topological indices. In addition, as more intensity data is used in calculating Qp,l2, the experimental error is diminished naturally. Thus, Qp,l2 can be used to easily and accurately characterize LG modes.