Objective To investigate the characteristics of bone marrow megakaryocytes in patients with idiopathic thrombocytopenic purpura (ITP) complicated with positive for antinuclear antibody (ANA) but cannot be diagnosed as rheumatic immune diseases. Methods Newly diagnosed ITP patients in the First Hospital Affiliated to Sun Yat-sen University were retrospectively selected and divided into ITP1 group (ITP patients with positive ANA) and ITP2 group (ITP patients with negative rheumatic indicators). Degree of thrombocytopenia, the total number of bone marrow megakaryocytes, and the ratios of various types of megakaryocytes at the initial diagnosis were compared between the two groups. Results A total of 42 newly diagnosed ITP patients were included, with 20 cases in the ITP1 group and 22 cases in the ITP2 group. There were no significant differences in general information such as gender and age between the two groups (P>0.05). The platelet (PLT) count was (7.55±0.96)×10⁹/L in the ITP1 group, which was lower than (10.23±1.21)×10⁹/L in the ITP2 group, but there was no significant between-group difference (t=1.697, P=0.097). Compared with the ITP2 group, the total number of megakaryocytes in the ITP1 group was significantly decreased (t=3.071, P < 0.01), and the ratio of granular megakaryocytes was significantly increased while the ratio of naked nuclear megakaryocytes was significantly decreased (P < 0.05); there were no significant differences in the ratios of immature and platelet-producing megakaryocytes between the two groups (P>0.05). Conclusion Patients with ITP and positive ANA have a tendency of decreased PLT, and a more significant maturation disorder of bone marrow megakaryocytes, with a lower degree of megakaryocyte proliferation compared to patients without positive ANA. ANA may exacerbate the severity of ITP by aggravating the developmental disorder of bone marrow megakaryocytes.