The principles of three commonly frequency domain digital watermarking algorithms were introduced, of which were discrete Fourier transform algorithm (DFT), discrete cosine transform algorithm (DCT), and discrete wavelet transform (DWT). Digital watermark information was embedded into the carrier image with the three algorithms. The values of peak signal-noise ratio (PSNR) and correlation coefficient (NC) were detected. The advantages and disadvantages of the three algorithms were analyzed and compared. It was proved that DWT algorithm can get the best effect.