In　order　to　simplify　the　driving　control　module　for　the　high　intensity　focused　ultrasound　phased　array　with　hundreds　of　elements,　a　phase-control　method　with　high　excitation　efficiency　is　proposed.　With　the　help　of　this　method,　focused　acoustic　fields　of　a　256-element　annular　spherical-section　phased　array　are　calculated　and　compared　with　the　corresponding　fields　obtained　by　using　the　traditional　control　method　of　imposing　both　amplitude　and　phase　signals.　It　is　shown　through　simulation　and　experiments　that　the　therapeutic　focusing　fields　with　spatial　single-focus　can　be　synthesized　validly,　under　the　conditions　of　simplified　driving　control　module　and　increased　array　excitation　efficiency.　The　focal　energy　aberration,　which　is　brought　with　this　simplification　method,　can　be　compensated　validly　by　adjusting　the　overall　input　acoustic　power.