Abstract: Studies of nuclear exotic decay and structure around the drip line are of critical importance for understanding new laws in nuclei and developing new nuclear theories. In recent years, significant progress has been made in related research. However, there are still numerous new phenomena and mechanisms, which need further exploration. In this paper, the two-proton decay of resonant states in ^16\rm Ne is used as an example to introduce the applications of the invariant mass method in proton decay studies. With the invariant mass method, the decay energies and the corresponding momentum correlations of the ground state and the first excited state in ^16\rm Ne are determined. Comparative analysis with results obtained using the decay-in-flight method has illustrated that the invariant mass method, with its complete kinematic measurements, offers more precise results about the decay characteristics of resonant states. By simulating invariant mass spectra under the assumption of different half-lives for the ground state of ^16\rm Ne, the impact of nuclear lifetime on the accuracy of the invariant mass spectrum is studied. The results indicate that the invariant mass method is effective and reliable for short-lived nuclei, while the decay-in-flight method is more suitable for long-lived nuclei.