The existing low bit rate multi-channel audio coding schemes basically depend on parametric model related to the psychoacoustics. On this basis, this paper aims at the linear microphone array, in which the redundancy between the array topology and signal is inventively exploited so that the coding efficiency is improved well. Compared with the classical schemes, the new parametric coding scheme proposed here effectively minimizes the amount of space parameters that need to be transmitted and greatly save the cost of transmission resources. Subjective and objective tests show that the perceived quality is nearly stabilized with substantial transmission cost reduction.