A signal detecting method and a receiver using the same are provided. The method includes the following steps. A receiving signal vector y is received through a number of channels, wherein the receiving signal vector y corresponds to a transmitting signal vector x transmitted by at least one of the channels. A channel matrix H is determined, wherein the channel matrix H represents at least one of the channels. A factorization matrix D is chosen, wherein D is invertible to make the channel matrix H expressed as H={tilde over (H)}D, and {tilde over (H)} is a corresponding channel matrix. The factorization matrix D is determined to make an expected value of the signal estimate error become smaller. The receiving signal vector y is detected to estimate the transmitting signal vector x according to the corresponding channel matrix {tilde over (H)} and the factorization matrix D.