Objective To investigate the effects of diazoxide (DIA)cardioplegic solution on the reduction of donor cardiomyocyte apoptosis, Methods In a Krebs-Henseleit (KH) solution perfused isolated rabbit heart Langendorff model, 32 rabbit hearts were divided into four groups with simple random sampling (8 rabbits in each group ): DIA group (50μmol/L diazoxide mixed in KH solution),STH group (ST, Thomas' solution), 5-HD group (50μmol/L diazoxide and 100μmol/L 5-hydroxydecanoic acid mixed in KH solution), KH group (KH solution), The rabbit hearts of each group underwent 6 hours of hypothermic (4 C) storage in the corresponding cardioplegic solution. Left ventricular developed pressure (LVDP), maximal values of positive rate of left ventricular pressure (+dp/dtmax) were measured before and after storage, The post-storage values of LVDP and +dp/dtmax were expressed as the percentage of pre-storage control values. Apoptotic cardiomyocytes were detected by the TdT- mediated dUTP-biotin nick end labeling (TUNEL). Malonaldehyde (MDA) contents and adenosine triphosphate (ATP) contents were also measured after storage. Results Recovery rates of LVDP, +dp/dtmax, and ATP contents in DIA group were higher than those of other 3 groups respectively(P〈0. 05), Cardiomyocytes apoptosis percentage and MDA content were lower than other 3 groups respectively(P〈0. 05), Conclusions Diazoxide cardioplegic solution can protect the isolated hearts and this may be relates to opening selective mitochondrial KATP channels. The selective mitochondrial KATP channel antagonist 5-hydroxydecanoic acid can block the cardioprotective effect of diazoxide.