Pyrolysis mass spectrometry (pyrolysis-MS) offers chemically and physically rich insights into polymer materials. However, its broader application has been limited by the inherently non-quantitative nature of MS, primarily due to ionization-efficiency variability among fragment species. To overcome this limitation, we present a reference-free, datadriven analytical framework that enables robust quantitative analysis without requiring any pure-component reference spectra. By eliminating the need to prepare actual standard materials, this approach allows system components to be flexibly defined—including virtual or hypothetical entities—based on the analytical objective. As a result, phenomena previously considered incompatible with conventional compositional analysis, such as monomer sequence distributions and degrees of polymer degradation, can now be quantified within a unified framework. This advancement transforms pyrolysis-MS from a qualitative diagnostic into a versatile quantitative tool, offering new capabilities for thermal analysis, material design, and lifecycle evaluation in polymer science.