Photomagnetic materials have attracted enormous attention due to the adjustable coloration and magnetization via light irradiation, while challenges still exist for drastically tuning the magnetism at room temperature. Herein, a novel multifunctional crystal complex (H3-TPB)[Fe(C2O4)3]·H2O (1; C2O42–= oxalate and TPB = 1,3,5-tris(4-pyridyl)benzene) is constructed by self-assembly of paramagnetic Fe3+ions, electron donor oxalate, and electron acceptor TPB ligands. After light irradiation, the compound 1undergoes unidirectional electron transfer (ET) from oxalate to TPB ligands and Fe3+ions, which not only results in the decomposition of oxalate and generation of radicals and Fe2+species but also leads to remarkable ET-triggered photochromism. Importantly, room temperature light irradiation changes the magnetic behavior of 1from weak to strong antiferromagnetism. Moreover, thanks to the stability of the photogenerated radicals, the photoresponsive proton conductivity property for 1is also explored and photoenhanced proton conductivity is observed after photoirradiation.