1. A channel estimation method based on a time-domain training sequence at a signal receiving end of a terrestrial digital broadcast system, comprising: x. acquiring a first initial channel vector from a receiving signal vector received by the signal receiving end, the first initial channel vector used for channel estimation of a current frame of the received receiving signal vector; y. calculating a second initial channel vector and a third initial channel vector, the second initial channel vector being calculated using a training sequence vector contained in the receiving signal vector and a transposed training sequence vector that is a transpose of the training sequence vector, and the third initial channel vector being calculated using the transposed training sequence vector and the receiving signal vector; a. performing channel estimation of acquiring each channel estimation value by a conjugate gradient method, the conjugate gradient method using the first initial channel vector, the second initial channel vector, the third initial channel vector, and a preprocessing matrix; and b. performing noise reduction processing on each channel estimation value to acquire a final channel estimation value based on a first predetermined threshold value.