Channel-specific property of polar coding deteriorates error-correcting performance once the channel is time variant or the estimation of bit-channels is inaccurate. Therefore it restricts the feasibility of polar codes on several applications. One of the solutions is channel-aware construction of polar codes, which adjust the construction to match the current channel on the fly. To reduce time and space complexity, the channel-awareness is executed only for the bit-channels in window size. However, how large enough for a window size is ambiguous in literature. In this paper, two algorithms are proposed to optimize the window size of channel-aware polar codes. In addition, the performance of channel-aware polar codes with practical constraints and channels are provided. The experiment results show that there is almost no performance loss when the practical issues are considered, and the advantage of channel-awareness would be obvious in practice.