Abstract: In view of the optimal load-shedding control with transient stability constraints,a parallel pattern search algorithm is adopted to effectively solve this problem.As a gradient-free optimization algorithm,this method can avoid the difficulty in calculating the sensitivity or gradient of transient stability constraints on the control variables with complicated models.It is easy to realize without the convergence problem.For the repeated calculation of transient stability,the power system simulator for engineering is used for dynamic simulation,thus combining the simulation software available with the optimal algorithm,increasing the flexibility of simulation models and methods,as well as the reliability of the results.Meanwhile,the mission of transient stability calculation is rationally allocated by the framework of parallel search,increasing the search speed of the algorithm.The test results of three cases of different scales show that the algorithm can reliably give the load-shedding strategy.