Hi @ljvmiranda921, sorry for reply late, I was busy with other things and forgot to check the progress here. As you said, these values take the token index , not the character index. I have fix the bug when I replace character index with token index. Everything works fine now. And in case you might need it, the vocab.txt is the same as the "bert-base-cased" in huggingface transformers. Thanks again for you advice and I will try to write a "validator" to check the input data next time.