A terahertz(THz) all-metal metasurface with a high Q-factor has been proposed, consisting of four diamond-shaped holes. By altering the size of adjacent diamond-shaped holes, the symmetry of the structure can be broken, resulting in quasi-Bound states In the Continuum(BICs). By changing the polarization angle of the incident wave, the frequency of the excited quasi-BICs remains unchanged, exhibiting polarization-independent characteristics. Simulation results show that, by optimizing structural parameters, when the size deviation is 3 μm, the quasi-BICs achieved an ultra-narrow bandwidth of less than 1 GHz, corresponding to a Q-factor greater than 1 300. Experimental test results show that the fabricated sample(with a deviation of 30 μm) had a measured Q-factor of 40. Compared to circular hole structures, the diamond-shaped hole structure can achieve stronger bound fields due to its sharp corners. The proposed metasurface with polarization-independent quasi-BICs has enormous practical application potential in real-time chemical and biomolecular sensing.