A comprehensive error analysis is carried out for a 256-element annular spherical-section phased array when used for synthesizing three\|dimensional multi-focus acoustic fields. The influence of array excitation errors on field patterns is summarized for both amplitude and phase errors. References to the design of driving module are provided for phased array with hundreds of elements. The simulation results show that the phased array with hundreds of elements has a robust ability of acoustic field synthesizing. Five-bit digitalization of phase signal can ensure the validity of the abstained acoustic fields. The array excitation errors affect the focal energy distribution mostly. The effect of amplitude errors can be weakened by reducing the error ratio through increasing the overall excitation energy.