A power pool online precaution control method based on the static state and the transient safe stable mode, includes: 1) obtaining the transient state process, 2) seeking the transient state and the static state safety margins, 3) performing the pattern classification to the failure, 4) trying to the obtain the adjusting project which satisfies all the failure modes, 5) computing the participation factor of the unsafe candidate control measurement of the transient state voltage and the frequency and sorting, 6) computing the sensitivity of the participation factor of each overload candidate control measurement after the failure and sorting, 7) obtaining the new mode data after adjustment and checking the safety of the static state and the transient state. The invention performs the coordination optimization among the transient power angle, the transient voltage / frequency and the static state device overload precaution control through integrating the control measurement participation factor of each mode, obtains the optimized safe and stable precaution control measure for satisfying the practical requirement of the engineering.