An antenna module and a mobile terminal are provided. The mobile terminal has a metal frame and a system grounding spaced apart from the metal frame. The antenna module has a radiating body formed in the metal frame and a parasitic element coupled to the radiating body. The radiating body is configured for generating a main harmonic, and the parasitic element is configured for generating a parasitic harmonic. The antenna module further has a first tuning circuit connected in series between the radiating body and the system grounding, and a second tuning circuit connected in series between the parasitic element and the system grounding. The antenna system has at least four operation modes. The antenna system of the present invention may cover the LTE low, medium and high frequencies as a single antenna. A flexible and convenient method for tuning the antenna module is also provided.