The origin of the cosmic singularity and vacuum zero-point energy, long-standing puzzles in Big Bang cosmology challenging current physical frameworks, remain central issues in modern physics. Based on the Cosmic First Principles, this study establishes "Electric Primitives" and "Magnetic Primitives" as the ultimate quantum primitives of the universe, constructs the "Cosmic Theory of Electric Primitives and Magnetic Primitives", and proposes a phase transition-driven mechanism for singularity evolution. Key findings: True Vacuum consists of Primordial Unities formed by the symmetric fusion of Electric Primitives and Magnetic Primitives; False Vacuum is composed of Electric Primitives, Magnetic Primitives, and Electromagnetic Primitives—all generated from phase transitions of Primordial Unities. Together, these structural features reveal the microscopic origin of vacuum zero-point energy. Their self-organization drives phase transitions, the Big Bang, and spacetime evolution. The logical consistency of the proposed phase transition mechanism and cosmic evolution framework is verified via thought experiments, providing theoretical operability for interpreting unobservable early cosmic processes. This study establishes a theoretical bridge linking quantum primitives to cosmic evolution, offering a groundbreaking framework for resolving the mystery of cosmic origin and advancing the unification of quantum mechanics and relativity.