The invention discloses a speed controller parameter optimization method in consideration of primary frequency modulation and ultralow-frequency oscillation suppression. According to the method, a single machine infinite system containing an optimized unit and an equivalent infinite power supply is established, a comprehensive optimized index function is established under the stimulation of frequency step signals of the primary frequency modulation test requirement by regarding the unit openness/power response curve rise time, stabilization time and reverse regulation power as performance indexes of primary frequency modulation and regarding damping torque coefficients of a speed controller and a water turbine system in an ultralow frequency band as ultralow-frequency oscillation damping performance indexes, the primary frequency modulation performance and the damping level can be considered by obtained speed controller parameters, and technical means is provided for optimization of the speed controller parameters and suppression of ultralow-frequency oscillation.