The invention relates to a box girder of a bridge crane. The box girder is mainly made of carbon fiber composites and sequentially comprises a lining layer, an adhesive coating, a fiber-laid composite inner layer, a fiber-laid composite middle layer, a fiber-laid composite outer layer and a glass fiber cloth outer protective layer from inside to outside. In the manufacturing process, a girder lining is provided firstly, then the adhesive coating is smeared on the outer surface of the girder coating, and the fiber-laid composite inner layer, the fiber-laid composite middle layer and the fiber-laid composite outer layer are sequentially laid on the outer surface of the adhesive coating; then the glass fiber cloth outer protective layer prepared from 90-degree glass fiber prepreg is laid on the outer surface of the fiber-laid composite outer layer; and then the laid girder is heated and cured. By the adoption of the box girder of the bridge crane and the manufacturing method of the box girder, the weight of the girder can be greatly reduced, the strength, the rigidity and the stability of the girder are improved, and accordingly the performance of the girder is improved.