The invention discloses an installation method for cabins and side walls of cargo tanks. The method comprises the steps that cargo tank supporting bases are installed at the preset fixing positions of the outer side walls of the cargo tanks, and cabin supporting bases are correspondingly installed at the preset fixing positions of the inner side walls of the cabins; actual coordinates of each cargo tank supporting base and the corresponding cabin supporting base; according to the differences between theoretical coordinates and the actual coordinates of the carbon tank supporting bases and the differences between the theoretical coordinates and the actual coordinates of the corresponding cabin supporting bases, the thickness and the installation positions of base plates are obtained; according to the obtained thickness of each base plate, the base plates are manufactured, and according to the installation positions of the base plates, the manufactured base plates are installed on the cargo tank supporting bases or the cabin supporting bases; each cargo tank is suspended into the preset installation positions inside the cabin. It is ensured that the supporting bases on the side walls of the cargo tanks and the supporting bases on the cabins can be effectively assembled, and therefore normal installation of the cargo tanks and the cabins can be ensured.