Abstract: Objective　〖JP2〗To establish a stem-loop method for peripheral blood microRNA-21（miR-21） detection in peripheral blood monocytes（PBMC），and primarily apply the method into bronchial asthma patients.   Methods　According to the sequence of miR-21，the stem-loop reverse transcription primer and the primer of polymerase chain reaction（PCR） were designed and synthesized. The expression levels of miR-21 in PBMC of 20 bronchial asthma patients and 20 healthy subjects were measured by SYBR green real-time fluorescence PCR with U6 as control. The difference between the 2 groups was analyzed. Results　The melting curve of U6 and miR-21 in the 2 groups showed a single peak by SYBR green real-time fluorescence PCR，and the product of PCR was specific. The miR-21 levels in PBMC of 20 bronchial asthma patients were significantly higher than those of 20 healthy subjects（P＜0.001）. Conclusions　The method of detecting miR-21 expression levels by SYBR green real-time fluorescence quantitative PCR is established successfully in PBMC. Moreover，it provides the basic reference for molecular-biology research of miR-21 in bronchial asthma.

Key words: Micro RNA-21, SYBR green real-time fluorescence quantitation, Bronchial asthma