Forming diversified global supply chains (GSC) is an important approach to improving economic resilience. When firms expand their oversea suppliers for such purposes, information friction is a major challenge, and internetization may help firms cope with it by more efficient communication of information. We introduce a dynamic discrete choice model for firms’ searching for new supplier sources estimated with structural methods, and construct counterfactual studies to analyze the internetization effects on Chinese firms’ GSC diversification. Our quantitative studies reveal that internetization relieves information friction, which reduces firms’ searching costs by 13.4%, and thus significantly diversifies firms’ GSC. It also raises firms’ productivity by 0.5% through efficient communication of information. Reductions in searching costs are revealed as the main channel of such effects of internetization, while the productivity channel is less significant. Moreover, the internetization effects on diversifying GSC are persistent over time, and are biased towards high-productivity and importing firms.