We experimentally investigate the broadband partially coherent light focused by a focusing lens and especially the chromatic aberration effects of a focusing lens on the spectrum of the focusing light field at the geometrical-image plane. The experimental results show that,compared with the spectrum of the incident light, the normalized spectrum of the partially coherent light, at the geometrical-image plane, takes on blueshift at some observation points and redshift at others. In splits into two peaks at some observation po particular, the normalized spectrum of light nts,and the spectral shift changes rapidly at the critical point, i. e. the spectral switch occurs. Furthermore, each of the two peaks of the normalized spectrum still splits into two peaks at some points,and the spectral switch occurs again in the short-wavelength range of the normalized spectrum at the critical point. These results of investigation are significant to the high-precision measurement of spectrum and the research of new-style spectral switch.