Megawatt power impact frequently occurs during experiments on magnetic confinement fusion devices. This power impact, which shows the features of high amplitude, rapid change, and strong randomness, threats to the stable operation of fusion devices when achieving long-pulse high temperature conditions. To more effectively handle such power impact, the precise and real-time detection of impulse power is indispensable. Aiming at the issue, the quasi-proportion resonance (QPR) algorithm based on adjustable damping factor is developed, which realizes good extraction and high-speed response performance. Combined with the reference phase angle of grid voltage, the active and reactive power can be further divided. Considering the harmonic power with various frequencies included in impulse power, the cascaded quasi-proportion resonance (CQPR) detection strategy is proposed, which compensates for the deficiency that QPR is unable to handle multi-frequency impulse power. Finally, the validity and stability of CQPR algorithm are proved by MATLAB and experiments with Digital Signal Processing (DSP) platform.