According to the polarization characteristics of the thin film narrowband filter, the stack of narrowband filter used in oblique incidence is provided based on the genetic arithmetic in this paper. A 100GHz five-cavity thin film filter used in 18° incidence is optimized based on the programme. The stack can eliminate the phenomenon of polarization light central wavelength separation used in oblique incidence and it has low polarization dependent loss. It can be used as an angle-tuned thin film filter for wavelength modulation. Compared with the thin film filter stack obtained by needle arithmetic design, it has higher rectangle degree, larger wavelength tunable range and less polarization dependent loss. The experimental results show it meets the demand of design and its tunable range is more than 25 nm.