Metamaterials with I-shaped metal structure units have abnormal electromagnetic properties. The finite difference time domain (FDTD) method is used to simulate the I-shaped metamaterials. It is found that there are three special reflected modes in symmetric I-shaped structure. When the symmetry of the structure is broken and the slit length increases, a new mode appears, respectively, and five specific reflection modes are in the structure. Theoretical model is developed and physical causes of formation of the five reflection modes are analyzed combing near field distribution. It is believed that different position resonance couplings of surface plasmons in the I-shaped metal structure units lead to the five specific reflection modes. When the symmetry of the structure is broken, new resonant mode appears. When the slit length increases, high order resonance mode appears.