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 an initial channel vector used for channel estimation of a current frame; wherein the channel estimation method further comprises: y. calculating an algorithm initial vector based on a training sequence vector contained in a received receiving signal vector and the receiving signal vector; a. based on the initial channel vector and the algorithm initial vector and using a conjugate gradient method based on a preprocessing matrix, performing channel estimation to acquire each channel estimation value; and b. based on a first predetermined threshold value, performing noise reduction processing on each channel estimation value to acquire a final channel estimation value.