Among the Vietnamese customs of early 20th century, besides the documentation written in Sino, there were also not a small number of documentation written in Nôm. To use Nôm script was with a clear purpose for “the ease of the people’s reading and understanding”. Nevertheless, there was a fact that in these documentation written by Nôm, Sinowas also appeared quite a lot. Sino script was used in many levels: word, Phrase, Sentence,Paragraph. Why Sino still appeared in Nôm documentation, while the editors themselves wanted to use Nôm for the readers’ easy understanding, and furthermore in the history context of Vietnamese society, it was the period of Sino declining? In addition to the too great impact of Sino language in Vietnamese language, were there any other reasons for that? Through the studying, the writer has found that the 4 said above levels were not used randomly, instead each level was used in one or some specified cases. The use of Sino in here was formed by 2 reasons: Habit; The fact that Sino was still psychologically more respected than Nôm, this was not erased in the conception of the editors.