In this paper, we propose a novel chaotic-based communication system with permutation index differential chaos shift keying (PI-DCSK) and spatial modulation (SM) technique. The SM can eliminates inter-channel interference by activating one antenna to transmit additional bits, while PI-DCSK can keep data secure and transmit more bits carried by permutation rules as compared to the conventional DCSK. Some of information bits are used to determine the index of the transmit antennas, and the rest are carried by PI-DCSK modulation. At the receiver, we use the Maximal Likelihood (ML) method to estimate antenna index and modulate bits to rebuild transmit bits. The theoretical and simulation results show that the proposed SM-PI-DCSK can enhance system efficiency and provide significant performance gains over the conventional chaotic-based schemes in multipath Rayleigh fading channels.