By selecting different types of thin plasma targets and applying two-dimensional particle-in-cell (PIC) simulation system, the acceleration behaviour of proton in the self-generated magnetic field induced by ultra intense laser and the thin plasma target interaction are studied. The results show that when the power density of interaction of intense laser is 1020 W/cm2, due to the self-generated magnetic field produced plasma target, the proton distribution exhibites space directional emission; the emission direction and the energy of the high energy proton are closely related to the plasma target surface. The higher proton energy, the smaller the divergence angle and the better proton accelerator effect are. In the round thin plasma target, the proton maximum energy reaches 41.1 MeV. This result has important application value for the inertial nano fusion fast ignition and tumour therapy.