Calligraphy is the treasure of traditional Chinese culture and it is ubiquitous in China. Because of the unique aesthetic characteristics of calligraphy, the difficulty of calligraphy teaching lies in the assessment of calligraphy works. The major problems concerning calligraphy assessment are the low time efficiency of calligraphy assessment and low engagement of students in the assessing process. As an active learning method, peer assessment (PA) has been widely applied to education. This research aims to explore the application of PA to the calligraphy class. With reasonable training, elementary school students can act rationally as an assessing group. On the basis of students' scores, this study further takes the most reasonable scores based on clustering analysis as the final score. Through the comparative analysis of the students' scores and the teachers' scores, it shows that the students' scores of calligraphy writing can obtain results that are close to the teachers' scores. The significance of the study lies in enhancing the time-efficiency of calligraphy assessment and maintaining the learners' high levels of engagement in the assessing process. The results show that the use of PA in the assessment of calligraphy writing is an effective and accurate method of calligraphy assessment, which contributes to students' command of the key points of calligraphy marking and plays an integral role in guiding students' future calligraphy practice.