The invention provides a grid processing method for adaptively processing a fluid flow velocity image with an obstacle. The grid processing method comprises the following steps: drawing a grid of s*s pixels from left to right and from top to bottom; when the width w of the obstacle in the grid is not smaller than 0.75s or when the height h is not smaller than 0.75s, drawing no grid at the position; when the width w of the obstacle in the grid is smaller than 0.5s, when the height h is smaller than 0.5s and when w is smaller than, moving the grid leftwards for w pixels; when w is not smaller than h, moving the obstacle in the grid upwards for h pixels; when the width w of the obstacle in the grid is not smaller than 0.5s and when the height h is not larger than 0.5s, moving the grid upwards for h pixels; when the width w of the obstacle in the grid is not larger than 0.5s and when the height h is not smaller than 0.5s, moving the grid leftwards for w pixels; when the width w of the obstacle in the grid is not smaller than 0.5s and is smaller than 0.75 s and when the height h is not smaller than 0.5s and is smaller than 0.75 s, drawing a plurality of rectangular grids in the grid with the obstacle in the grid removed, and using one grid having the largest area as the grid herein.