To achieve the manufacturing of Thin-Wall and High-Rib Components (TWHRC) with high precision, a novel heavy load Multi-DOF Envelope Forming Press (MEFP) with Parallel Kinematic Mechanism (PKM), driven by six Permanent Magnet Synchronous Motors (PMSMs), is developed. However, on account of the heavy forming load, the PMSM parameters are in great variation. Meanwhile, the PMSM is always in a transient state caused by fast time-varying forming load, resulting in low identification precision of varied PMSM parameters and control precision of PMSM under traditional parameter identification methods. To solve this problem, a novel Sliding Mode Control Method with Enhanced PMSM Parameter Identification (SMCMEPPI) for heavy load MEFP is proposed. Firstly, the kinematic model of MEFP is established. Secondly, the variation law of PMSM parameters under heavy load is revealed. Thirdly, an enhanced PMSM parameter identification method is proposed, in which the q axis current of PMSM is used to represent the changing rate of forming load and the adjustment factor is first proposed to remove improper input of PMSM parameter identification online. Fourthly, the Electromechanical Coupling Dynamic Model (ECDM) of MEFP, which includes identified PMSM parameters, is developed. Finally, based on the developed ECDM, a novel SMCMEPPI is proposed to realize the high-precision control of heavy load MEFP. The experimental results indicate that the proposed SMCMEPPI can significantly improve the control precision of heavy load MEFP.