The tissue distribution of DNA-PLGA-NP was investigated by the technique of gamma scintigraphy. The results showed that 30 min after mouse caudal vein injection of 32P-DNA-PLGA-NP, the ratio of radioactivity in liver against total radioactivity is higher than 70%, which is 1.4 fold the ratio after caudal vein injection of 32P-DNA, and that 2 h after subcutaneous injection of 32P-DNA-PLGA-NP 2 h, the ratio of the radioactivity in liver against total radioactivity is also higher than 70%, reaching a 1.6 fold increase when compared with the ratio after subcutaneous injection of 32P-DNA.