Based on Wyner tapping channel and the composite channel, the information transmission ability of a channel is considered in which legitimate transmission channel set is a classical channel and wiretap channel set is a quantum channel. The goal is to design coding and decoding scheme, so that the receiver can decode the message sent by the sender perfectly (decoding error probability close to zero), while the degree of confusion of eavesdropper to messages is as high as possible. On this basis, it is guaranteed that in the case of Alice′ s knowing of information of channel condition, there is the security capacity of classic composite channel when quantum wiretaps; at the same time, the lower bound of security capacity of this channel is known in the case of Alice′s unknowing of information t of channel condition.