Objective To investigate the optimal cell concentration of mouse cardiac microvascular endothelial cells (MCMECs) tubeformation in vitro, so as to establish a tubeformation system of MCMECs. Methods MCMECs were obtained by tissue block method. Isolated MCMECS were divided into four groups: 5×103 cells/well, 1×104cells/well, 2×104cells/well and 3×104 cells/well. The cells were cultured into Matrigel gelcoated 48well plates. They were and photographed under a microscope after 24 hours. Image J was used for detecting the number of lumens and branches， SPSS17.0 was used for data analysis.Results The method of tissue block can successfully cultivate mouse myocardial microvascular endothelial cells,and the isolated cells positive expression vWFrelated antigen. Lumen like structure was generated when cell concentration was 1×104/well, 2×104/well, 3×104/well，but no lumen like structure was generated when cell density was 5×103/well. When the cells concentration was 2×104/well, the number of lumens and branches were more than other groups（x-±s）.Conclusion The mouse myocardial microvascular endothelial cells have the abilityof tubeformation in vitro. Within a certain range of cell concentration, the higher concentration of inoculation cells, the more lumens and branches of tubeformation in vitro. However, after the cell concentration exceeds the optimal concentration, the ability of tube formation in vitro of mouse myocardial microvascular endothelial cells decreases with the increase of cell concentration.