To investigate the effect of multifunctional gold nanoparticles on radiosensitization and micro CT imaging in lung adenocarcinoma A549 tumor bearing mice. The tumor-bearing mice were treated with gold nanoparticles and irradiated with different energy levels of 160KV X-ray and 6MV X-ray, respectively. The tumor volume of each group was measured every time of treatment. The tumor-bearing mice were treated with gold nanoparticles via Intra-tumoral injection. The Micro CT scan was carried out at fixed time intervals to observe the imaging and deposition time of nano-gold in the tumor tissue. There were no significant differences between control group and gold nanoparticles group (P = 0.842) in tumor volume. Compared to the 6MV X-ray group, the 6MV X-ray combined with gold nanoparticles group resulted in a smaller tumor volume. But there was no significant difference (P = 0.96) between the groups. The tumor volume of 160kv X-ray combined with gold nanoparticles group was significantly smaller than that of 160kv X-ray group (P = 0.031). The Micro CT scan assay showed that the deposition time of nano-gold in the tumor tissue was 30 days. The effect of imaging was good, and no toxicity of gold nanoparticles was observed in this study. Multifunctional gold nanoparticles and 160kv X-ray irradiation exhibited significant radiosensitization effect in A549 cells-bearing mice. The stable CT imaging of the nano-gold in the tumor can be used as a potential method for mapping and delineating the target area of tumor-guided radiotherapy.