Traditional planar nearfield acoustic holography places the hologram inside the jet. In order to reduce the adverse effect of window effect and wraparound error on reconstruction accuracy, it is generally required that the hologram size is twice more than that of the sound source, while larger microphone array placed inside the jet will interfere with the stability of the jet. To solve this problem, it was proposed to place the entire hologram outside the jet. According to the classical shear layer correction theory, the changes of path and amplitude of sound wave propagating from sound source to hologram were analyzed. Then the modified sound field propagation formula was derived. Finally, the theoretical model of planar nearfield acoustic holography under the combined action of moving fluid medium with the Mach number below 0.3 and shear layer was established. Numerical simulations show that the improved planar nearfield acoustic holography leads to reconstructed acoustic fields of high resolution, with high localization accuracy of aerodynamic noise source and certain anti-interference ability.