The Finite Element Analysis(FEA)based optimization procedure aiming to obtain the optimum mirror parameters was first improved, it was found that the degradation of surface figure accuracy was mainly caused by spherical aberrations through Zernike polynomial surface fitting using 21 terms. After that, another duralumin prototype VCM (aperture 135 mm, central thickness 8mm and initial curvature radius 2 807 mm) was fabricated and tested. Because of the improvement of the fabrication process, the initial surface figure accuracy of the second mirror is superior to λ/80 (632.8 nm). When a pressure of about 0.07 MPa is imposed, the saggigus variation reaches nearly 37 μm and the corresponding surface figure accuracy is still superior to λ/40 (632.8 nm) with spherical aberrations removed. Compared with the first prototype VCM, the performance of the second one has been improved prominently.