Аннотация:The problem of stability of excited frequencies is considered for a ring doubly-resonant optical parametric oscillator. The theory developed is based on the fixed field approximation used to analyze the interaction of waves on the tip of resonator cavity. It is shown that the excited frequency fluctuations arising due to resonator parameter variations can be largely suppressed. The suppression coefficient of technical fluctuations can be equal to 10^3 and more.