Based on Log-MAP algorithm of easy engineering implementation, the two different methods of using extrinsic information, the Berrou and Robertson schemes, are studied deeply in the paper. The study points out that the two methods are consistent, and the only difference lies in the treatment to the scale of weight applied to the extrinsic information in iterative decoding. Under the same constraint condition, by Monte Carlo means the performances of Turbo codes with extrinsic information in different fashions are simulated, and the result shows that Robertson method is better than Berrou method from the overview.