Based on open quantum systems and non-equilibrium field dynamics, a unified physical theory connecting cosmic evolution and microscopic quantum decoherence is established. Two core axioms are proposed: the non-equilibrium field difference axiom provides the external rigid condition for the emergence of ordered structures, and the quantum intrinsic upward chemotaxis axiom describes the internal driving force for systems to evolve toward higher information integration and complexity. Using an ultra-low temperature global field and a local ordered microenvironment as an analog model, the underlying isomorphic logic of cosmic and life evolution is revealed. The theory is embedded into the open quantum system framework, and the intrinsic chemotaxis correction is introduced into the standard Lindblad master equation to construct a full quantum master equation at the density matrix level. The time-dependent effective decoherence rate Γₑբբ(t)=Γ−βαe⁻ᵅᵗ is rigorously derived, and the analytical solution of coherence decay C(t)=exp(−Γt+β(1−e⁻ᵅᵗ)) is obtained. The theory predicts that quantum coherence exhibits non-exponential stretched decay under ultra-low temperature and low noise conditions, which is falsifiably different from the mainstream pure exponential decay. The physical definitions and theoretical constraints of parameters β and α are clarified, and a semi-quantitative magnitude estimate is given (optimistic upper bound β≲10⁻⁶, to be determined experimentally). Four groups of controlled experiments are designed based on platforms such as superconducting qubits and ion traps, and four quantitative test criteria are proposed to evaluate the experimental feasibility. This theory defines the second law of thermodynamics as an effective law for macroscopic isolated systems, establishes intrinsic chemotaxis as the core driving force for directed evolution, and forms a complete logical closed-loop from unified physical framework and cosmic evolution model to microscopic experimental predictions.