The invention discloses a color domain space transforming method based on FPGA. The method includes steps of separating the processing course into five parts in parallel; receiving three RGB componentvalues of a pixel at a first part of a flow line and depositing; completing combination and subtraction operation at the second part of the flow line, and confirming the sequencing condition of the receiving three RGB component values of the pixel; valuating parameter required by the part beneath the flow line according to the sequencing condition of the three RGB components of the pixel and thealgorithm formula for transforming the RGB color domain space to the HSV color domain space at the third part of the flow line; using a division method module at a fourth part of the flow line and inputting the required parameter to the division method module; applying the output result of the division method module to calculate the values of three HSV components after transformation of the colordomain space at the fifth part of the flow line. The method has the advantages of greatly improving the transformation speed of the image color domain space and providing great convenience for the subsequent image treatment.