Counting and Photoshop pixel method were used to measure ferrite volume percentage of ER2209 duplex stainless steel layering, the result shows that ferrite volume percentage of layering respectively is 50.1% and 56.5% by counting and Photoshop pixel method, the values are in between 30% and 60%, the outcome meets to phase ration requirements. Standard deviation of ferrite volume percentage φα is 2.06% by Photoshop pixel method, but that is 4.89% by counting, compared with two methods, Photoshop pixel method is better to measure ferrite volume percentage of duplex stainless steel layering.