Objectives:To investigate the effects of thyroid hormone on L-type calcium mRNA and L-type calcium current of atrium and ventricle. Methods: Sixteen rabbits were randomized into Thyroxine group (n=8) and Control group (n=8). In Throxine group, rabbits were injected intraperitoneally with L-thyroxine solution for 2 weeks (1mg/kg·d-1) . In Control group, rabbits were injected with the same volume of saline as for Thyroxine group. On day 15, 4 rabbits in each group were killed for examing the L-type calcium current of atrium and ventricle using whole cell patch clamp and other 4 rabbits were killed for detection of L-type calcium mRNA using RT-PCR. Results: The mean peak of L-type calcium current [I_Ca,L] densities (pA/pF) at -10mV was higher in Thyroxine group than in Control group (-8.59±0.68 vs -6.54±0.49 in atrium, n=8, p<0.001; -8.85±0.50 vs -7.06±0.43 in ventricle, n=8, p<0.001 ). Conclusions: Supplement of thyroid hormone may ameliorate myocytes contractility in sepsis.