The invention relates to the field of aluminum base composite material processing, in particular to an extrusion process for a vehicle body in-situ nanoparticles enhancing aluminum base composite material. The vehicle body in-situ nanoparticles enhancing aluminum base composite material synthesized in situ under the outer field control is used as a research object, the casting defects such as holes and loosening are eliminated by adopting the hot extrusion plasticity, so that the texture is refined and dense, the extruded grains are uniform and small, and the mechanical properties are obviously improved; meanwhile, under the action of the extrusion pressure, the agglomeration particles are dispersed and dispersed in a matrix, the bonding force with the matrix is higher, a lot of dislocation is generated, a high-density dislocation mesh is formed, and dislocation enhancement is produced accordingly. The T4P+ artificial aging heat treatment of the follow-up extrusion material can eliminate the thermal residual stress caused by the different thermal expansion coefficients of nanoparticles and matrix in the process of the hot extrusion, the plasticity of the vehicle body extrusion material is further improved, and the vehicle body in-situ nanoparticles enhancing aluminum base composite material extrusion material which can replace the steel plate is obtained.