Currently there is no consensus on treating anemia in pregnant thalassemia patients. In China, Colla corii asini (CCA) has been widely used for treating anemia for more than 2000 years. However, its clinical application in the thalassemia population is limited by a lack of quantitative evidence. The present study aims to investigate the therapeutic effect of CCA in increasing hemoglobin (Hb) concentration and improving abnormal hemoglobin compositions in pregnant patients with β-thalassemia. Seventy-two pregnant patients who met inclusion criteria were randomly assigned to either the treatment group or control group. Patients in the treatment group were given 15 g of CCA, while the control group were observed and followed up without any treatment. Levels of Hb, serum iron (SI), serum ferritin (SF) and three types of Hb components [adult hemoglobin (HbA), fetal hemoglobin (HbF), minor adult hemoglobin (HbA2)] were measured before and after treatment. Treatment with CCA led to a significant increase of Hb. The major Hb component induced by CCA was HbA, while levels of both HbA2 and HbF dropped after treatment. CCA treatment significantly increased SI, while SF remained unaffected. Our data suggest that CCA can improve anemia and optimize Hb components in pregnant patients with thalassemia without affecting iron reserves.