Abstract: Based on micro focus high speed photography system, there are still lots of ambient noise and diffraction stripes caused by welding dust and arc light in the photos of the pulse GMAW (gas metal arc welding) droplet, which make the measurement of the droplet geometry, necking and other characteristic of droplets quantificationally more difficult. To ensure the property of the image before and after processing invariably, the linear image processing algorithm including the designed low pass attenuator and Gaussian low pass filter combined with gray level mapping and Laplacian addition was proposed based on frequency domain. The results of experiments show the combination of frequency domain calculation with linear image processing can obtain the clear photos of pulse GMAW droplet shape which separated from noisy background. The reality and availability of the photos is ensured. This method of also provides the possibility for pulse GMAW process high precision quantificationally analysis.