The invention provides a system and method for dynamic soft measurement of the molten iron silicon content in the blast furnace ironmaking process. The system comprises an actual data collection unit, a normalization pretreatment unit and a dynamic soft measurement unit. The method includes the steps that the parameters required by dynamic soft measurement of the blast furnace molten iron silicon content are obtained and comprise the operating parameters of the current furnace charge, the operating parameters of the previous furnace charge and the molten iron silicon content of the previous furnace charge; normalization pretreatment is conducted on the obtained parameters required by dynamic soft measurement of the blast furnace molten iron silicon content; and dynamic soft measurement of the molten iron silicon content is conducted through a model of dynamic soft measurement of the molten iron silicon content in the blast furnace ironmaking process. Compared with existing manual measurement or analysis of the molten iron silicon content, the workload of operators is reduced, measurement uncertainty introduced by manual operation is lowered, measurement timeliness and accuracy are improved, and the confidence level is high. The method has universality in prediction of the molten iron silicon content in the blast furnace ironmaking process, and closed-loop integrated control over the blast furnace molten iron quality and optimized operation can be achieved easily.