The invention discloses a layered soft rock tunnel asymmetric support structure and a construction method. The layered soft rock tunnel asymmetric support structure includes a tube shield support perpendicular to the bedding surface direction of layered soft rock, a tube shield support which is not perpendicular to the bedding surface direction of the layered soft rock, a steel arch, a mortar boltperpendicular to the bedding surface direction of the layered soft rock, a mortar bolt which is not perpendicular to the bedding surface direction of the layered soft rock, a pressure-type anchor cable, an upper step feet-lock bolt, a lower step feet-lock bolt, an inverted arch initial support, initial shotcrete and a secondary lining. According to the layered soft rock tunnel asymmetric supportstructure and the construction method, the asymmetric support structure is adopted, for a layered soft rock strata with different dip angles of the bedding surface, the support structure is strengthened in the direction perpendicular to the bedding surface where extrusion failure is more prone to occurring, the stress state of the tunnel support structure can be effectively improved, the construction method is still based on a traditional upper and lower step reserved core local method, additional workload is avoided, and while meeting the tunnel support requirements, the time is maximally shortened, and the economic cost is maximally saved.