With ［Si］ time series of No. 1 BF at Laiwu Iron and Steel Group Co. and No.6 BF at Linfen Iron and Steel Group Co. as sample space, and based on rescaled range analysis and method of box dimension, the Hurst exponents of ［Si］ time series of these two BFs and the box dimensions are figured out to be ranging from 0.257 and 0.224 and 1.712 and 1.724, respectively. The complex degree of ［Si］ time series is described, and it is also proved that ［Si］ time series is a long-term negative association fractal time series. With the correlative parameter fixed, the simulated trend was pictured by the theory of iterated function system.