To address the issue of the grating lobes and side lobes of the acoustic field of two dimensional sparse ultrasonic phased array, the formula for calculating the directivity of two dimensional sparse ultrasonic phased array is deduced, and the transmit array and the receive array are interleavingly placed to eliminate grating lobes and suppress side lobes. After optimization, the transverse and lateral scanning ranges have been expanded from 30° to 60°. Considering the effect of the damaged element on the directivity of acoustic field, the function of the acoustic field directivity versus the position of the damaged element is established. the acoustic field simulation analysis shows that the element errors near the array center result in a maximum increase in side lobes of 20 dB, and the main lobe decreases 6 dB independent of the location of the damaged element. When the damaged elements of the transmit array and the receive array are in the same place, the influence on array directivity reaches its maximum.