Abstract: In this paper, a multifunctional metasurface based on photosensitive semiconductors is proposed, which can exhibit three functions of absorption/polarization conversions. Without pump light illumination, the metasurface operates in dual-band absorption mode with the absorptivities of 95.1% and 94.4% at 2.25 THz and 2.75 THz, respectively. When the metasurface is illuminated by the 1 550 nm pump light, it works in broadband polarization conversion mode with the polarization conversion rate（PCR） of above 90% and the relative bandwidth of 47.8% in 1.32 THz～2.15 THz frequency band. When the metasurface is illuminated by the 800 nm pump light, it works in dual-band polarization conversion mode with the PCRs of over 90% in two bands of 1.09 THz～1.23 THz and 2.12 THz～2.23 THz. The physical mechanism of different modes is explained by analyzing the magnetic field and surface current distributions. The proposed metasurface may be useful in future multifunctional terahertz devices.