The degree of polymerization of paper cellulose is one of the key factors affecting paper’s lifetime and mechanical properties. Research on the degree of polymerization of handmade paper is important for dating ancient paper and evaluating the quality of restoring paper. In our work, we used Yingchun, Zhuma, Yuanshu and Longxucao papers as the model substrates of mulberry bark, ramie, bamboo and Eulaliopsisbinata papers, respectively, to study the applicability of the copper ethylenediamine (CED) method for the detection of handmade paper, and to further investigate the effects of lignin content, dissolution time and the presence or absence of air on the intrinsic viscosity of paper. The results indicate that the CED method is suitable for the determination of handmade paper with a lignin content below 10%. The intrinsic viscosity and degree of polymerization of handmade paper can be calculated from the actual concentration of cellulose after subtracting the lignin content. In the dissolving process, paper should first be impregnated in water for 2 hours, which will shorten the dissolution time. In addition, air should be excluded during the test to prevent the degradation of cellulose and to improve the accuracy of testing results.