In order to know micron focal switch of polychromatic TEM22 mode Hermite-Gaussian (HG) beams passing through an apertured dispersion lens system, numerical calculation examples were used to study the beam’s intensity distributions. The data of the axial intensity distributions were achieved. It is found that variation of the bandwidth results in change of two maximal intensities of TEM22 mode (HG) beams and thus position of the principle maximal intensity shifts rapidly. When relative bandwidth γ is 0.231 and Fresnel number Fw is 100, the position varies 2.5μm and the phenomenon of micron focal switch presents. The bandwidth and Fresnel number are important factors that induce the micron focal switch. A narrow bandwidth is enough to induce the focal switch of TEM22 mode (HG) beams in the system with large Fresnel number whereas a broad bandwidth is required in the system with small Fresnel number. Results in this paper help the design and manufacture of micro and nano optical devices in optical communication technique.