Cassava starch is mainly composed of amylose and amylopectin which can be hydrolysed to glucose, fructose, maltose or others derivative valuable things. Ultrasound treatment is a non-conventional method of starch degradation. This method generates micro jet effect with high local temperature and pressure which can produce radical ion to degrade the starch. Ultrasound energy transferred to liquid is proportional with ultrasound amplitude. Therefore, this study was focused on the effects of ultrasound amplitude of cassava starch to enhance the production of reducing sugars. Concentration of (1/20 (w/v)) cassava starch suspension was prepared by adding starch in aquadest. Direct ultrasonic probe was immersed in suspension and operated at a temperature of 35°C in 10 minutes and 60 minutes for various amplitude (30% - 70%). The product was analysed by Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) and DNS method. From the experiment result, ultrasound treatment of cassava starch has a significant effect on structural disorganization in morphological characteristics and decrease the degrees of crystallinity of processed starch. The production of reducing sugar is directly proportional to the amplitude of ultrasound treatment. The highest reducing sugar concentration of 0.114mg/mL were obtained for cassava starch with ultrasound treatment at 40% of amplitude for 60 minutes.