The invention discloses an OFDM timing synchronous system based on a noise subspace, comprising a fast Fourier transformation device, a phase compensation and conciliation device, a fast Fourier inverse transformation device, a square device, an addition device and a window minimum searching device, wherein the fast Fourier transformation device, the phase compensation and conciliation device, the fast Fourier inverse transformation device, the square device, the addition device and the window minimum searching device are sequentially connected. By introducing a noise subspace concept, the influence on an estimation result by multipath intersymbol interference is removed, thereby unbiased timing synchronous information can be obtained; and the Fourier positive/inverse transformation device has the characteristics of a high-efficiency implementation structure and a fast algorithm, and the system implementation complexity is reduced by adopting large numbers of Fourier positive/inverse transformation devices. The timing synchronous system can be used for various block mode transmission systems including OFDM, with cyclic prefixes.