Glass preform is able to affect form of abnormal aspherical lens as its irregular shape. Different preforms were investigated by numerical simulation to discuss how to affect form of abnormal aspherical lens. A typical abnormal aspherical lens was chosen as target lens, and the globular and cylindrical glasses were chosen as preforms. Using advanced nonlinear finite element program of MSC.Marc, the form process of the abnormal aspherical lens was simulated. Based on the simulations, the formability, the residual stress and the form precision were analyzed and compared. It can be inferred that the glass preform of cylindricity is more suitable for forming abnormal aspherical lens.