The work aims to study the structure optimization and cooling effect of the logistics box used in the transportation of fresh food. A detachable logistics box with cold plate was designed. It consisted of a cold plate, a shell layer, a thermal insulation layer and a contact layer; and the physical model for the cooling effect of the logistics box was set up. The cooling effect under different conditions was analyzed in the finite element method. The relationship between the heat flow density on the surface of logistics box and the thickness of the thermal insulation layer was obtained by the polynomial fitting method. It was found that, when the air temperature outside the logistics box was 25 ℃, if the thickness of thermal insulation layer was 15 mm, the heat flow density of the surface of the box was about 20 W/m2 higher than that of 25 mm. The designed logistics box can be reused for many times, convenient for the use of space in the box and the placement of goods. The analyzed results help select the proper thickness of thermal insulation layer at the time of designing the logistics box.