目前用入射光束束宽等于出射光束束宽时对应的功率为空间孤子临界功率的方法，寻找到的功率通常不是唯一的，甚至大部分是形成呼吸子的功率。通过分析束宽随入射功率的变化曲线(W-P曲线)，提出在W-P曲线的束宽变化的转折区域来寻找孤子临界功率的理论。用此理论拟合了实验测得的铅玻璃中出射束宽随入射功率变化的数据，准确地得到了铅玻璃中形成孤子的临界功率。

Presently it is believed that the incident power is just the critical power of the nonlocal spatial solitons when the output beam width equals the input the beam width. The power decided by this method is generally not one and only, even is the power of breather. A theory is brought forward that one should find the critical power of the solitons on turning area of the curve of output beam width versus the input beam power. According to this theory, the experimental data obtained in lead glass are fitted, and the exact value of the soliton critical power is obtained.