The sound field separation technique based on single surface measurement is investigated in this paper. A modified separation formula based on the spatial Fourier transform is presented to overcome the inherent singularity of the current single surface separation technique. However due to the wraparound error associated with fast Fourier transform （FFT）, the accuracy of separation technique based on FFT is not satisfactory and a novel separation method based on the statistically optimized nearfield acoustic holography is proposed to improve the separation. The simulations as well as experiments carried out with the p-u intensity probe produced by Microflown demonstrate the validity of the proposed modified formula and the effectiveness of the new separation method.