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为研究六硝基六氮杂异戊兹烷（CL‑20）的高温热膨胀及相变规律，采用分子动力学方法和价角势能截距修正的ReaxFF‑lg反应力场，考察了ε‑、β‑和γ‑CL‑20的相变温度和热膨胀系数。为验证力场适用性，计算了常温下三种晶型CL‑20的密度、晶胞参数、晶格能和升华焓。采用三阶Birch–Murnaghan状态方程拟合了0~280 GPa压力范围内ε‑CL‑20的p‑V曲线，得到体积模量及随拟合压力升高的变化规律。高温相变分析表明，ε‑和γ‑CL‑20在398~423 K产生相变，其中ε→γ相变在常压下发生，而γ→ε相变需加压0.5 GPa以上；β‑CL‑20在448 K下转变为ε晶型。热膨胀系数分析表明，ε‑CL‑20高温热膨胀过程无明显各向异性，而β‑和γ‑CL‑20分别在c方向和b方向表现出各向异性。研究结果表明，修正的ReaxFF‑lg反应力场适用于ε‑、β‑和γ‑CL‑20的高温高压相变研究，对于β‑和γ‑CL‑20的热膨胀研究精度有待进一步提高。“,”In order to analyze high temperature phase transformation of hexanitrohexaazaisowurtzitane （CL‑20）， phase transformation temperatures and coefficients of thermal expansion of ε‑， β‑， and γ‑CL‑20 were studied via ReaxFF‑lg reactive force field molecular dynamics， with modified valence potential intercept. To validate the applicability of selected force field，the density， cell constant， lattice energy， and sublimation enthalpy for three types of CL‑20 at room temperature were calculated. The third order Birch‑Murnaghan equation of state was used to fit the p‑V curve of ε‑CL‑20， with pressure ranging from 0 to 280 GPa. And the variation of bulk modulus （B0） and its partial derivative to pressure （B′0） with the increase of pressure is analyzed. High temperature phase transformation analysis shows that ε‑and γ‑CL‑20 change phases at 398-423 K， of which the ε→γ phase transition occurs at atmospheric pressure， while the γ→ε phase transition needs 0.5 GPa or higher pressure； β‑CL‑20 transforms to ε crystal form at 448 K. The thermal expansion coefficient analysis shows that there is no obvious anisotropy in the high temperature thermal expansion process of ε‑CL‑20， while β‑ and γ‑CL‑20 show anisotropy in c direction and b direction， respectively. Results show that the modified ReaxFF‑lg reactive force field is suitable for the study of phase transition of ε‑， β‑， and γ‑CL‑20 at high temperature and high pressure， while the accuracy of thermal expansion of β‑ and γ‑CL‑20 needs to be further improved.