Solution polymerization mechanisms and kinetics of 4,4′-bismaleimidodiphenylmethane (BMI) with trithiocyanuric acid (TCA) in n-methyl-2-pyrrolidone (NMP) were investigated. A competition between the aza-Michael addition reaction and free radical polymerization occurred, and the reaction system competed with the predominant aza-Michael addition reaction. Model-free in differential form method was used to determine activation energy along fractional conversion. In addition, the model-fitting approach was adopted to assess compensation effect parameters for the activation energy and pre-exponential factor. Then, triplet kinetic parameters were achieved. The average activation energy and frequency factor were approx. 94 kJ mol−1 and 1.45 × 1012 min−1, respectively, in the fractional conversion (α) range 0.1–0.9, and the reaction-order model, f(α) = (1 − α)0.81, was of choice. Importantly, these triplet kinetic parameters could effectively predict kinetic curves for the isothermal reaction BMI and TCA.