We propose a new data smoothing method for near-field acoustic holography (NAH) with the aid of the data extrapolation. This method can reduce the error energy which comes from the finiteness of the measurement aperture. We illustrate our calculational results by using of the computer simulations which apply to the numerically generated data by Fast Fourier Transform (FFT). The simulations show that the error energy leads to zero after 30 times iteration of extrapolation algorithm. Our calculations show that our data smoothing method is applicable for the quantitative analysis of the vibration energy in the NAH signal processing.