In this paper, we investigate the capacity of known interference channel, where the receiver knows the interference data but not the channel gain of the interference data. We first derive a tight upper bound for the capacity of this known-interference channel. After that, we obtain an achievable rate of the channel with a blind known interference cancellation (BKIC) scheme in closed form. We prove that the aforementioned upper bound in the high SNR regime can be approached by our achievable rate. Moreover, the achievable rate of our BKIC scheme is much larger than that of the traditional interference cancellation scheme. In particular, the achievable rate of BKIC continues to increase with SNR in the high SNR regime (non-zero degree of freedom), while that of the traditional scheme approaches a fixed bound that does not improve with SNR (zero degree of freedom).