Abstract: Fractal theory has been increasingly used in rock mechanics problems. The specific surface area of the aggregate is often calculated by image processing technology, however the operation is cumbersome and easy to produce error, and the specific surface area of aggregate and the aggregate gradation cannot be linked. Based on the fractal theory, the particle size distribution, gradation, volume and surface area of the aggregate were correlated and a calculation method of aggregate specific surface area was derived. Combined with the gradation curve of artificial aggregates in the dry land of the Baihetan Hydropower Station, the specific surface area of the finished materials with different grades was calculated. The results show that the specific surface area of the 80~150, 40~80, 20~40, 5~20 mm graded product are 22.57, 30.75, 60.44, 150.06, respectively. The calculated values are consistent with the measured value. The aggregate particle size has a great influence on the fractal dimension and specific surface area of the aggregate. The finer the graded aggregate, the larger the specific surface area, and they have power function correlation. The error between the calculation result and the software processing result is about 10%, showing that the fractal surface theory can accurately calculate the specific surface area of the artificial aggregate.