Quantum Fisher information plays a central role in the fields of quantum metrology and quantum precision measurement. However, quantum systems are vulnerable to the influence of noisy environments, which degrades the precision of parameter estimation (as measured by quantum Fisher information). Therefore, overcoming the influence of environmental noise has become an important scientific issue in quantum precision measurement to enhance the quantum Fisher information of parameters. In this work, we investigate the enhancement of phase estimation precision for a two-level atom subjected to a zero-temperature bosonic environment, using a continuous null-result measurement scheme. We derive an analytical expression for the final state of the atomic system after n null-result measurements. To emphasize the crucial role of continuous measurement in the dynamics of a two-level atom, the core amplitude coefficient in the final state is reformulated into a specific form, resulting in a concise mathematical expression. Interestingly, we find that the dynamics of the two-level atom under continuous measurements are closely related to a scaling parameter—the product of the environmental spectral width and the measurement time interval. In certain special cases, this formulation reduces to known results such as the quantum Zeno effect and Markovian approximations. Furthermore, we demonstrate that under both Markovian and non-Markovian conditions, the quantum Fisher information for the atomic phase estimation can be significantly enhanced by adjusting this scaling parameter. Using an exactly solvable model, we also provide an explanation for the quantum Zeno effect without explicitly using the projection postulate. We find that in certain limits a concise formula for \tildeh(t) = h^n(\tau) accurately captures the numerical results across a broad range of parameters. In summary, the proposed frequent null-result measurement scheme for post-selection of the environment effectively mitigates the adverse effects of decoherence on quantum Fisher information, providing a novel theoretical approach for achieving high-precision measurements in open quantum systems.