The scattering intensity at 720 nm (I720) is chosen as the optical parameter of evaluation，and we use the dual point optical parameters far from the center to evaluate the thermal damage near the center during the process of laser thermal damage. Firstly, we test on the laser thermal damage of in vitro porcine livers to collect I720 in real time at points which are 4, 8, 12 mm far from the heating center, and laser heating is stopped when I720 at 8 mm rises to 6 times compared with its initial value (group A). We conduct twenty experiments to calculate rising multiple of I720 at 4 mm far from the center with the mathematical model using the parameters of heating time, rising multiples of I720 at 8 mm and 12 mm. Secondly, we repeat the above thermal damage experiments and real-time data acquisition when the condition of stopping heating is I720 at 4 mm rising to 3, 4, 5, 6 times (group B). Ten experiments are done for each condition, and forty experiments are established. Finally, the slice analysis on samples of group B are taken to establish the relationship between the rising multiples of I720 and the damage effect. The results show that the accuracy is above 90% when heating time and rising multiples of I720 at 8 mm and 12 mm are used to estimate rising multiple of I720 at 4 mm. It is feasible to evaluate the effect of laser thermal damage in real time at a point near the damage center by dual-point optical parameters far from the center.