Abstract: Objectives To investigate the relationship between nasopharyngeal carcinoma hypoxia degree evaluated by imaging of the marker(99m)technetium-labeled 4, 9-diaza-3, 3, 10, 10-tetramethyldodecan-2, 11-dione dioxime(^99mTc-HL91) and tumor regression in medium-term radiotherapy. Methods 34 patients with nasopharyngeal carcinoma staging from Ⅱ-IVa underwent ^99mTc-HL91 SPECT imaging, integrated CT scan and its image fusion one week before receiving radical and continuous radiotherapy. Tumor/muscle, tumor/cerebra of the nasopharyngeal carcinoma and lymph node/muscle, lymph node/cerebra of the neck lymph node metastases were calculated, and lesion regression degree was measured in medium-term radiotherapy. Results ① The diameter of nasopharyngeal carcinoma with positive hypoxia imaging was(1.70±0.68)cm. There was a positive relationship with tumor/muscle and tumor/cerebra(r was 0.607 and 0.640, P was 0.001 and 0.000). ②There was significant difference between tumor/muscle and tumor/cerebra(P was 0.004 and 0.001) of nasopharyngeal carcinoma with grade I and grade ID regression. The regression degree of nasopharyngeal carcinoma in medium-term radiotherapy was negative correlated to the hypoxic degree(tumor/muscle:r=-0.602; tumor/cerebra:r=-0.643, P<0.01), ③^99mTc-HL91 imaging detected 28 neck metastasis lymph, nodes. There was no significant line trend between lymph node/muscle, lymph node/cerebra of Lymph node metastases and its size, lesion regression degree in medium-term radiotherapy. Conclusions The Larger the nasopharyngeal carcinoma, the higher the hypoxia degree of lesion, and the less regression in medium-term radiotherapy. There was no significant relationship between hypoxia of neck lymph node metastases and its size and medium-term regression.