Although the Joseon mathematical treatise Dongsancho is officially attributed to an anonymous author, it is widely presumed to be the work of Hong Jeongha, based on its striking similarities to his authenticated work, Guiljib. This study aims to verify the connection between the two treatises through a comparative analysis. By examining their structure and contents, this research not only confirms significant similarities but also identifies some differences. These variations shed light on Hong Jeongha's focus as a mathematician during the six-year interval between drafting Dongsancho in 1718 and completing Guiljib in 1724, specifically in his structural approaches utilizing approximations of irrational numbers, Tianyuanshu, and Kaifangshu. By establishing the validity of the argument that Dongsancho served as a draft for Guiljib, this study concludes that Dongsancho was indeed authored by Hong Jeongha as a preliminary manuscript. Based on these findings, it is anticipated that future studies in the history of Korean mathematics will formally attribute Dongsancho to Hong Jeongha, dated 1718.