The new spread ALOHA system based on the multi level transmission technique is proposed. The spread ALOHA system with the three-valued signaling and Code Shift Keying (CSK) are combined in the proposed system. This system can reduce the packet length of the spread ALOHA system without extension of the frequency bandwidth. It is expected to improve the system performance. In this paper, the throughput performance of the proposed system are evaluated by theoretical analysis. Moreover, throughput performances of the spread ALOHA systems without CSK are compared. It is shown that the proposed system is superior to conventional spread ALOHA systems when E b /N 0 is larger than 10[dB].