Abstract: Objective To study the immunohistochemical characteristics of the bronchofiberscope-guided pathological biopsy specimen in small cell lung cancer (SCLC) patients. Methods A total of 65 SCLC patients confirmed from January, 2014 to January, 2017 in our hospital were selected. The clinical pathological results and immunohistochemical characteristics were analyzed. Results The SCLC occurred in 42 male cases and 23 female cases, respectively. The age was (57.1±2.6) years old. 45 cases had the smoking history. The male ratio was significantly higher than that of female ratio (P<0.05); the histological types, age, positions of tumor and pathological staging for the different genders of patients were not significantly different (P>0.05). The positive rate of CD56, TTF-1, CK and Syn in the SCLC patients was 90.77% (59/65), 81.53% (53/65), 69.23% (45/65) and 73.8% (48/65), respectively. The patient's ratio with Ki-67 index ≥ 60% was 76.9% (50 cases). The patient's ratio with Ki-67 index ≥ 60% was 51.6% (16 cases) at the limited stage and 82.35%(28 cases) at the extensive stage. The related percentage at the limited stage was significantly higher than that at the extensive stage (P<0.05); the positions of tumor, histological types and pathological staging in the other phenotypes of SCLC patients were not significantly different (P>0.05). Conclusion Smoking is one of the major risk factors of SCLC that is majorly occurred at the extensive stage. The immunohistochemical index of TTF-1, CK, CD56, Ki-67 and Syn are of great importance to the final diagnosis of SCLC. The majority of the SCLC patients have the Ki-67 index ≥ 60%, that are majorly occurred at the extensive stage. Therefore, the Ki-67 index ≥ 60% can be considered as the important prediction indicators on the clinical assessment and prognosis of SCLC. It shall be recommended in clinical practice.