Human bone marrow is the major source of mesenchymal stem cells (MSC). It was reported that the standard density gradient centrifugation method was not efficient in isolating MSC and it may be caused by the existing of bone marrow particles. In previous study, a lot of MSC were obtained by culturing bone marrow particles alone combined with standard method. However, it is time- and labor-consuming to obtain bone marrow particles by filtering and to isolate MNC by density gradient centrifugation. This study was purposed to explore the more simple and efficient method to isolate MSC from bone marrow. Seven normal bone marrow aspirates were collected and centrifugated. The bone marrow particles floated on surface layers were cultured by modified primary explant culture, whereas the bone marrow aspirates deposited were cultured by direct plating method, then the immun phenotype and differentiation capability of isolated cells were analyzed. The results showed that in 3 of 7 aspirates, bone marrow particles were floated on surface layers, whereas the other bone marrow cells and some particles were deposited after centrifugation. The MSC were reliably isolated from the floating layers or deposited aspirates by modified primary explant culture and direct plating method separately. After 3 passages the isolated MSC did not express CD45 and CD34, but expressed CD105, CD73, CD44, CD90, CD49e and they could differentiate into chondrocytes and adipocytes. It is concluded that normal human bone marrow MSC can be isolated simply and efficiently by direct plating method in combination with modified primary explant culture.