A transmission method executed in a multiple input multiple output wireless communication system may include the following steps: receiving a transmitting bit sequence; providing an X level pulse amplitude modulation (X-PAM) signal set, wherein distances between any two adjacent signal points in the X-PAM are the same; generating M signal sets according to the X-PAM signal set, wherein the ith signal set is formed by multiplying the X-PAM signal set with a parameter (1/X)(i−1), wherein i is an integer from 1 to M, and generating a X-PAM signal set joint coding/decoding table according a superposition result of the M signal sets; generating M transmitting bit sub-sequences according to the transmitting bit sequence; generating M transmitting signals according to the M transmitting bit sub-sequences and the X-PAM signal set joint coding/decoding table; transmitting the M transmitting signals to a wireless transmission channel via M transmitting antennae.