The invention discloses a cement-based silt lightweight roadbed block, a structure and a construction method. The cement-based silt lightweight roadbed block provided by the invention solves the problem of large waste of cement resources due to the need of on-site pouring for roadbed construction in the prior art, and has the beneficial effects of facilitating road construction and shortening theperiod of construction. The cement-based silt lightweight roadbed block provided by the scheme of the invention is as follows: a cement-based silt material is used as a roadbed block material; each roadbed block is a regular body; the peripheral sides of each roadbed block are respectively provided with a diagonal plane, so a first drainage channel is formed between every two roadbed blocks afterthe two roadbed blocks are spliced; the bottom side of each roadbed block is also provided with a second drainage channel along the length direction or the width direction of each roadbed block; and the directions of first drainage channels and second drainage channels are mutually perpendicular.