The coolant flow in the core of the supercritical water reactor experiences drastic change (e.g. density) near the pseudo-critical point, which may be susceptible to density wave oscillation instability, so the stability is a great challenge to the supercritical water reactor. In the paper, the method of frequency domain analysis was used to study the stability of the fast spectrum zone. The stability boundary was given, and sensitivities of some parameters such as mass flow, system pressure drop, axial power distribution and hot channel division were generated. The result shows that a high mass flow and a high system pressure drop are beneficial to the system stability. The higher power density of a hot channel is, the worse stability of the system is. These results can provide a little guidance to the supercritical water reactor core design and optimization.%在混合能谱超临界水冷堆中,冷却剂通过堆芯过程中跨拟临界点引起的密度等参数的剧烈变化易导致系统产生密度波振荡而不稳定,因此混合能谱超临界水冷堆的稳定性对系统的安全性至关重要.本文利用频域法研究快谱区的流动稳定性,给出在不同状态下的稳定性边界,同时对冷却剂入口流量、进出口压差和通道划分等对稳定性的影响进行了分析.结果表明:大的入口流量有利于系统的稳定；高的进出口压差对系统稳定性有利；轴向功率均匀分布较非均匀分布系统的稳定性差,可提供保守结果；热通道的功率密度越大,对系统的稳定越不利.研究结果对超临界水冷堆设计和优化有一定指导价值.
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