The present study was to evaluate the value of miRNA-30a in plasma as potential tumor marker in detecting breast cancer (BC). Using a novel approach to extract miRNA-30a from the plasma followed by real-time quantitative polymerase chain reaction (RQ-PCR) analysis, levels of miRNA-30a were quantified in plasma specimens of 100 BCs and 64 age-matched and disease-free healthy controls (HC). And we compared the diagnostic value of plasma miRNA-30a with conventional circulating tumor markers CA153 and CEA. The median levels of miRNA-30a were significantly lower in preoperative BC than those in HC (P < 0.001). The levels of CEA and CA153 were all significantly higher in preoperative BC compared with those in HC (P = 0.008 and P = 0.001, respectively), and only the level of CA153 decreased in postoperative BC compared with preoperative BC (P = 0.015). ROC analysis showed the sensitivity and specificity of miRNA-30a for BC diagnosis at 74.0 and 65.6 %, respectively, whereas the sensitivities of CEA and CA153 were 12.0 and 14.0 %, respectively. The status of ER and triple-negative BC was significantly associated with miRNA-30a level (P = 0.007 and P = 0.005, respectively). And no other clinicopathological features were found to had significant difference. Our findings suggest that plasma miRNA-30a decreased in patients with BC and has great potential to use as novel biomarkers for BC diagnosis.