Phase effect of orthogonal modes on the 3-dB axial-ratio beamwidth (ARBW) is investigated with pin-loaded patch antenna under different excitation schemes in this paper. Four shorting pins are introduced along the diagonals of the square patch at first, so that the electrical size of patch will be tuned for wide 3-dB ARBW. Next, as for the dual-fed CP patch antenna, the phase difference of port excitation is directly altered to observe its effect on 3-dB ARBW. And then, as for the single-fed CP patch antenna, which is loaded with two additional shorting pins as perturbation segment, varied phase difference is achieved by changing the pin spacing. After extensive simulations, the results of the two antennas show good agreement. It is demonstrated that the 3-dB ARBW will be widened in one of the principal planes but narrowed down in the orthogonal plane simultaneously, if the phase difference of two modes is not exactly 90°.