The invention discloses Q345FRD fire-resisting and earthquake-proof hot rolling angle steel used for public steel structure buildings and a preparing method of the Q345FRQ fire-resisting and earthquake-proof hot rolling angle steel. The preparing method of the fire-resisting and earthquake-proof hot rolling angle steel includes the following steps that A, molten iron is subjected to pretreatment desulfuration; B, molten iron is smelted; C, deoxidation alloying is conducted; D, LF furnace refining is conducted on the molten iron; E, molten iron casting is conducted; F, a steel billet is heated; G, the steel billet is subjected to high-pressure water tank scale removing; H, breakdown mill pre-forming is conducted; I, universal mill continuous rolling is conducted; J, angle steel online boundary dimension detection is conducted; and K, finishing is conducted. By means of the Q345FRD fire-resisting and earthquake-proof hot rolling angle steel used for the public steel structure buildings and the preparing method of the Q345FRQ fire-resisting and earthquake-proof hot rolling angle steel, due to integrated innovation on multiple technologies, microalloy element precipitation strengthening and refined crystalline strengthening mechanisms are given into full play, and the 345 MPa level number 14-number 18 hot rolling angle steel with high overall size precision, stable mechanical performance and good fire resistance and earthquake resistance performance and low-temperature impact toughness is produced, and the use requirement for fire resistance and earthquake resistance of the public steel structure buildings (such as automobile station yards, train waiting halls and motor train stations is met.