The invention discloses a bituminous pavement structure based on traffic condition of soft foundation and heavy load and a subgrade processing method. The bituminous pavement subgrade processing method based on traffic condition of soft soil foundation and heavy haul comprises the following steps: (1) determining the traffic level of road surface structure to be Special Level 1, Special Level 2 or Special Level 3 according to the standards of accumulative equivalent axles and the ratio of trucks with more than four axles on one lane; (2) determining the subgrade work zone depth of the SpecialLevel 1 and Special Level 2 to be 180-200cm and the work zone depth of the Special Level 3 to be 200-250cm; (3) determining earth pad strength level of the Special Level 1 is S4, S5 and S6; (4) processing the subgrage in the work zone depth with the method of laying mixed dregs, geogrid and detritus from bottom to top; (5) laying road surface. The method of the invention can improve the modulus of resilience of the road surface structure by 100-200%, lower deflection by 50-80% and save comprehensive cost of construction by 12-27.8%.