This paper mainly deals with problems of optimal field pattern control to the field conjugate direct synthesis of phased-array ultrasound hyperthermia. First,the rational optimal objective function for acoustic field pattern is put forward. Then, two optimal algorithms for global optimization are proposed. One is the genetic algorithm for constructing acoustic field pattern control and the other is the eigenvector algorithm for the same purpose. The simulation is performed with these two algorithms, genetic algorithm and eigenvector algorithm. Eventually, the objective of optimal field pattern control is achieved successfully. The genetic algorithm has better characteristics as compared with the eigenvector algorithm.