Based on the preliminary investigation and focused on the corona poling technology for modified PMMA films, some practical and operable way are proposed to enhance the poling efficiency and the second-order nonlinear optical effect of the films. For universal uneven distributions of the polarization field in traditional single-pin corona poled systems, a novel multi-pin corona poling structure is introduced and implemented. After a series of the polarization field simulations in different multi-pin structures, making use of finite difference method, a four-pin structure is determined as the most optimized for corona poling. The influences of the distance between the corona pin and the ground electrode, the number and arrangement of multipin on the distribution and efficiency of polarization field are also analyzed in detail. And then with single-pin and four-pin corona poling instruments, some polarization experiments for a modified PMMA/DR1 film were carried out, under different polarizing voltages and other optimized conditions. The results show that the four-pin corona poling structure is of great benefit to the improvement of polarization field distribution and efficiency.