Purpose This study aims to analyze the gait characteristics of the elderly patients with lumbar spinal stenosis by an intelligent device for energy expenditure and activity (IDEEA) to assist clinical work. Methods A total of 98 subjects were included in this study from January 2017 to December 2018. A total of 49 elderly outpatients with symptomatic lumbar spinal stenosis in unilateral lower extremity were included as the experimental group, and another 49 healthy subjects matched with gender, age, and body mass index (BMI) were analyzed as the control group. The gait data of the subjects (including single support, double support, SLS/DLS, swing duration, step duration, cycle duration, pulling accel, swing power, ground impact, foot fall, foot off, push off, speed, cadence, step length, and stride length) were collected to compare between the experience group and control group, the affected leg and the healthy leg in experimental group. Results The results of this study presented that small intermittent claudication occurred in all patients. The time of single support was significantly increased (p < 0.05). Double support, step duration, and pulling accel were increased (p < 0.05), and the Push off, speed, step length, and Stride length were decreased (p < 0.05) in the experimental group compared with the control group. Conclusion Small intermittent claudication was the basic gait composition of the elderly patients with lumbar spinal stenosis that can reflect the abnormal gait characteristics by IDEEA.