The gradation characteristic of ferronickel slag was analyzed by static image method and sieving method. The median, average particle size, standard deviation, skewness and peak of particle size of ferronickel slag were calculated by the Udden-Wentworth particle size division method and the Folk-Ward graphic method. Comparing with the sieving method, the content of coarse particles measured by static image method is larger than that measured by sieving method, and the content of fine particles will be small. The median and average particle sizes are coarse, sorting preference, skewness and peak value are sharp. The accumulative curve of size frequency of nickel-iron slag based on Φ value can satisfactorily reflect the characteristic of the particle size distribution. The repeated direct shearing test of nickel-iron slag was carried out with a large direct shearing instrument, and the particle gradation before and after shearing was compared, the result is expected to provide reference for the reuse of some industrial slag such as nickel-iron slag.