In this paper, we propose a tunable polarization-insensitive multi-frequency and broadband absorber (TMBA) based on a phase change material, which is vanadium dioxide (VO2). Compared with the prior works, the operation state of such a TMBA can be regulated by the temperature. When the temperature is 350 K, the proposed TMBA can act as an broadband absorber, whose absorption region (absorption is over 90%) runs from 10.04 to 16.22 THz at normal incidence. When the temperature is 300 K and the incident angle is normal, such a TMBA can work as a multi-frequency absorber that has five absorption frequency points exceeding 90%, which are situated at 6.11 THz, 9.51 THz, 12.81 THz, 16.07 THz and 17.55 THz, respectively. To figure out the physical mechanism, the electric field, the surface current and the power loss density of the TMBA are presented, and effect of incident angle and structural parameters on the performance of this TMBA also is given. The results show that, with the incident angle increasing, the absorption of this TMBA is reduced. Such a TMBA can be used as a solar energy harvesting.