Purpose This study was aimed at determining the effect of trunk stabilization exercises on walk speed and energy consumption during walk in chronic stroke patient. Methods The study used a single subject research design(ABA) and the subject in this study was a 55 year old man with right hemiplegia after stroke. The exercises program were modified from preceding studies and compromised of core muscle strengthening exercise and pelvis tilt exercise. The subject performed exercise program five times a week, one hour a day, four weeks. Pre base line(A) was only collected participant information without intervention in 5 times. Trunk stabilization exercise(B) was carried out 10 times and 5 times to base lime(A) after intervention. The walk velocity of the subject was evaluated by the 10m walking test, the energy consumption was measured by the oxygen cost as the oxygen consumption per unit distance and energy expenditure index as the difference of heart rate, in a session. Results The results of the analysis indicated that the 10MWT, Oxygen cost, Energy expenditure index were improved from 0.38m/s to 0.48 (26.31%), 0.41ml/kg/m to 0.34ml/kg/m(17.07), 0.97beat/min to 0.76beat/min(21.64%), respectively, from the baseline phase to intervention phase. The results indicated that the gait velocity improved and decrease oxygen cost, decrease energy expenditure index. Conclusions Therefore core strength exercise was effective intervention for improving energy efficiency during gait in chronic stroke patient.