The invention discloses a single-antenna orthogonal frequency division multiplexing-based spectral domain signal transmission device and a single-antenna orthogonal frequency division multiplexing-based spectral domain signal transmission method. A transmission processing unit is embedded in the device, and comprises an inverse Fourier transform unit, NT shunt-wound power allocation units, a cyclic displacement processing unit, an adder and a cyclic prefix unit, wherein the power allocation units are used for performing power allocation on signals; the cyclic displacement processing unit comprises NT parallel cyclic displacement units, and performs displacement processing on the output signals of the NT power allocation units according to the principle of one-to-one correspondence to obtain NT displacement signals; the adder is used for accumulating the NT displacement signals to obtain a summation signal; and the cyclic prefix unit is used for attaching a cyclic prefix to the summation signal, and feeding the summation signal attached with the cyclic prefix into a single transmission antenna for transmission. The single-antenna device regulates and controls an orthogonal frequency division multiplexing signal cyclic autocorrelation function by a cyclic delay vector, reduces the requirements of the transmission device on the number of radio frequency antenna modules, and reduces the hardware development cost.