OBJECTIVE The present study describes an improved in vitro culture method for obtaining high purity, vital and fully functional cardiomyocytes from neonatal rat. METHODS After cutting ventricular tissue with improved method, ventricular tissues were digested with low concentrations of trypsin overnight at 4 °C, and then underwent collagenase II digestion. Thereafter, cardiomyocytes were purified by combined differential adhesion and chemical inhibition methods. RESULTS Adherent cardiomyocytes were seen at 12 h after culture, spontaneously beating cardiomyocytes were observed at 24 h after culture, crosslinked cardiomyocytes were found at 48 h after culture, adhesion clustered cardiomyocytes were seen at 72 h after culture, dense network formed from inter-connected was evidenced together with radial arranged cell clusters and cell pseudopodia 96 h the mutual contact woven into and formed radically ordering cell clusters and island-like beating cardiomyocytes at 96 h after culture. The cell survival rate and purity were more than 98%. CONCLUSIONS Fully functional spontaneous beating cardiomyocytes can be obtained by the use of this improved primary neonatal rat cardiomyocytes culture method.