Abstract: On the basis of the large-scale corpus, this paper describes the diversified patterns and the diachronic changes of the lettered words in the text, and probes into the mechanism behind them. It is suggested that the use of means of signification can provide some or all semantic information for lettered words, which is an effective means to solve the difficulty of semantic comprehension. The study of the use of the means of signification shows that the frequency of the use of the means tends to decrease with the increase of the time of the use of the lettered words, driven by the principle of "saving effort". The article also briefly discusses the phenomenon of using the means of signification of loanwords.