Utilizing both analytical and numerical methods, this study examine unconventional photon blockade in a second-order nonlinear system influenced by two-photon absorption environment. First, we derive the optimal conditions necessary for achieving unconventional photon blockade through analytical methods. The numerical results for the equal-time second-order correlation function are then presented. Results indicate that unconventional photon blockade is present in the second-order nonlinear system affected by two-photon absorption environment, with the analytical optimal conditions aligning closely with the numerical results. Finally, an analytical expression for the equal-time second-order correlation function is provided and compared with the numerical results. The comparison reveals that the theoretical predictions for the equal-time second-order correlation function are largely consistent with the numerical results, and in regions of discrepancy, the theoretical values tend to be lower than the numerical ones. This inconsistency arises because the analytical calculations truncate the system's Hilbert space to two-photon excitation. In addition, the width of the photon blockade window increases with stronger external driving forces, whereas it decreases with greater second-order nonlinear interaction strength. These findings offer valuable theoretical guidance for the experimental observation and practical application of photon blockade in this system.