In recent years, many Vietnamese and International researchers have been interested in two aspects of Vienamese variant Chinese charaters – International variants and national variants. International variant characters here are Chinese characters originating from China. National variant characters are Chinese characters created by each country under the Chinese cultural influence, such as Vietnam, Korea and Japan. In order to clarify the charateristics of Vienamese unique variant Chinese charaters (national variants), we analyzed two Buddhist texts: The first one is Chư phẩm kinh 諸品經 (there are 187 variant Chinese charaters correspond to 183 standard charaters with total number of appearance is 1,697); the second one is Thích thị bảo dỉnh hành trì bí chỉ toàn chương 釋氏寶鼎行持秘旨全章 (there are 56 variant Chinese characters correspond to 41 standard characters with total number of appearance is 243).

Variant Hán characters (hereinafter referred to as variants) are a common phenomenon in various types of Hán-Nôm cultural materials, including Confucian documents. This article studies the variants in Confucian works through the case of the book Hồ thượng thư gia lễ/胡尚書家禮/Family rituals by Minister Hồ (printed in 1739). The author chooses this text because of the following factors: First, the content of this work, which might be described as Confucian in nature, is about Confucian rituals; Second, the text printed in 1739 is associated with clearly identified dates of production and chief commissioner, so variants found in this text have historical value; Third, this is a printed text, so its variants must have attained a degree of common usage. On that basis, the objectives of this article are: First, to provide statistics on variants, to classify their structures and to analyze some variation rules of this type of characters; Second, to provide preliminary comments (relying upon the above-mentioned data and analysis) on the flexible use of Hán characters by Vietnamese Confucian scholars in the 18th century.