Based on the multi-beam interference principle, a Gaussian beam reflected-intensity expression on a non-parallel angle-tuned thin-film filter in oblique incidence is derived. The influence of the reflected-intensity distribution with different incident angles, especially with different wedge angles of the non-paralleled thin-film filter is analyzed theoretically. Calculation and experimental results show that the reflected-intensity distribution, reflected-peak and the isolation degree are influenced by the wedge angle, incident angle and polarity of the wedge angle. In order to get stable reflected-characteristics and high isolation degree, the parallelism of the angle-tuned thin-film filter should be improved in fabrication or the polarity of the wedge angle in oblique incidence should be negative.