Optimization and coordination of under frequency load shedding（UFLS） and under voltage load shedding（UVLS） are hybrid optimization problem involving discrete and continuous variables， considering multi-condition， multi-scenario， multi-control-bus and multi-step-control. It has stability constraints of the high-dimensional， time-varying， nonlinear differential algebraic equations， including bounded stability of power angles and oscillation damping， as well as the excursion acceptability of algebraic variables. It is decoupled into the following four sub-problems: optimizing equipment placement by dynamically scheduling the control buses according to their integrated contribution degrees to insecure faults; dynamically scheduling the control buses according to their contribution degrees to single fault， iteratively optimizing the initial value of the first step in sequence of faults which are ranked based on effective control buses and security margins; optimizing load shedding of subsequent steps according to opportunity cost-performance ratio，with the sum of over-shedding risk and under-shedding risk of different faults in all operation conditions taken as the objective function; coordination between UFLS and UVLS by using decoupled optimization and iterative coordination. The effectiveness of the algorithm has been verified by the case of actual power system.