A wiretap channel is an important model for wireless communication. By applying an extended multiblock polar coding scheme, recent literature has achieved the secrecy capacity of a general wiretap channel (not necessary degraded or symmetric). However, this secure polar coding scheme of physical layer also limits the transmission rate of the main channel, which may fail to meet the demand of high transmission rate and strong transmission security for practical wireless transmission. In order to obtain a higher secrecy transmission rate than the physical layer coding scheme over a general wiretap channel, a cross-layer encryption and coding scheme is proposed in this paper. In the proposed scheme, an onetime-pad encryption and a secure key transmission is constructed by combining a chaos stream cipher with the extended multiblock polar coding scheme. As proved, the proposed scheme has achieved a high secrecy transmission rate than the former physical layer coding scheme under the constraints of reliability and strong security for a general wiretap channel.