The invention discloses an analysis method for improving modality and rigidity performance of an aluminum vehicle body based on a vehicle body joint. The method comprises the steps of using HyperMeshsoftware for carrying out finite element modeling, then grabbing key position joints in a vehicle body, establishing a joint structure finite element model, carrying out rigidity analysis under six working condition loads on a connecting element of each joint, and calculating the rigidity and the mode of the vehicle body are calculated through Nastran software; extracting a connecting piece in thekey joint for structure optimization; carrying out rigidity and modal calculation on the vehicle body for each optimization scheme to obtain an optimal optimization scheme; and conducting rigidity analysis on the key joint in the optimal optimization scheme, verifying the effectiveness of the optimization scheme through rigidity changes of the key joint before and after optimization, and therefore achieving the purposes of improving the vehicle sound rigidity and mode and reducing the overall weight of a vehicle body. According to the method, the scientificity, reliability and effectiveness of an optimization result are greatly improved, and a new idea is provided for a light-weight solution of the overall weight of the new energy automobile body in the field.