Hard pen calligraphy is the art of writing Chinese characters with hard pen. However, the concept of' hard pen' cannot be defined as the following two categories: one is semi-automatic writing tools created by western industrial civilization, such as pencils, pens, ballpoint pens, fountain pens, etc.; The other is traditional tools such as bamboo pens and feather pens, and it is difficult to confirm the source. The traces left by these two tools on paper and other media through various media have certain artistry and can be called "hard pen calligraphy". With the development of calligraphy, the artistry of lines has been paid more and more attention by the book circle. Shen Peng, a famous contemporary calligrapher, once said: "Among the elements of calligraphy performance, I value lines the most. Lines are the most important means and bridge from lines to verve, or genes. " The differences in calligraphy styles, calligraphers' fonts and the quality of calligraphy works are also related to the differences in line characteristics and levels. The creation of calligraphy works is first of all a unique discovery and creation of the beauty of lines. It can be seen that line is the gene of calligraphy, the symbol of calligraphy style and taste, and the first priority of calligraphy creation. Does the term line (or concept) apply to hard pen calligraphy? People often think that the pen line is thin, hard, revealing and simple, so we should give up or downplay the pursuit of its line and pay attention to the exploration of its knot, composition and charm. This view is a misunderstanding of "pen writing". The brush still talks about how to write a lot of big characters, and the pen also talks about how to write a lot of big characters with a thick pen. Compared with the written words, the main contradiction is that the pen is thin or the words are big. As far as the meaning of hard pen calligraphy is concerned, there should be a set of pens with different thickness and elasticity, plus carefully selected paper and pads. Facts can prove that pen lines can move from single to rich. The maturity of hard pen calligraphy lies in the perfection of its lines, which not only has the general attributes of calligraphy lines, but also has the unique characteristics of hardness and elasticity, thus forming independent hard pen calligraphy lines. The lines of hard-pen calligraphy are so important, but they are very weak in practice, so I want to make a systematic discussion on the nature, types and aesthetic value of the lines of hard-pen calligraphy in this paper, so as to attract more attention.