Modular trailer apply to transport large-sized, entire, extra long and super heavy cargo's fields. It can realize the double modes including full-trailer towing and semi-trailer towing. Under the former mode the max. speed of such trailer could reach 40km/h, and at this situation this towing way can get the max. tractive force and it is especially used in heavy duty transportation with low speed;semi-trailer towing can reduce the full length of the vehicle and the min. turning diameter, upgrade the effective load and speed of modular trailer while the max.speed of trailer could reach 80km/h as well.