Although the Chinese transcription of the The Secret History of the Mongols was systematically done observing quite reasonable principles, and those principles were applied with consistency to the most of the cases, there still exist lots of unexpected forms(less consistent, less correct, less efficient forms) in this invaluable Middle Mongolian text. It would be a very interesting task to search out those unexpected forms in the text, and figure out the reasons of inconsistency, incorrectness, and inefficiency in that it will be greatly helpful for the speculation on the linguistic identity of the participant(s) to the Chinese transcription from the original phonetic alphabet text, and the process of their transcription work, which have been the interests of the Mongolists all the time. Moreover, the results of this investigation may be utilized for the more correct linguistic reconstruction of the text, then we may expect to come nearer to the more correct knowledge of the Middle and Ancient Mongolian. This paper, in the first step of the investigation work on the whole text, made an observation on the usage of small characters 舌 and 中 which were used as diacritical signs, and the letters such as 古, 忽, 格, 客, 豁, 闊, 可, then speculated the reasons which caused those less consistency, less correctness, and less efficiency. As a result, this paper proposed the idea of ① hesitation-oscillation of the transcriber(s) at the native speaker`s level between the real pronunciations and the written forms of those days, ② mistakes by the secondary transcriber(s) who knew some Mongolian but not very well ③ as well as simple mistakes by the copyist(s)-engraver(s) who did not know Mongolian a t all. In the process of these works, such topics as latin transcriptions of leading scholars, questions on qahn-qaγan-qa`an and ka¨`u¨(n), intervocalic -g-, - γ- etc. were revisited.