This study was undertaken to evaluate the antioxidant activity of ethanolic extracts of eleven Myanmar medicinal plants. The crude ethanolic extracts of fifteen plant parts of eleven medicinal plants were screened for their activities. In phytochemical analysis and some mineral examination, the selected plants did not contain cyanogenic glycosides and arsenic The qualitative analysis of antioxidant activity of selected plant extracts using dot-blot DPPH staining was revealed the presence of significant antioxidant activity in the extracts of Cledronum siphonanthus (Leaves and Stalk), Curcuma longa, Garcinia mangostana, Heliotropium indicum (Stalk) indicated by the presence of yellow or white spot on TLC plate. The scavenging activity of ascorbic acid, positive control, was found about 94.25%. In in vitro DPPH free radical scavenging assay, Heliotropium indicum (Leaves) and Calotropis procera (Leaves) showed 84.54% and 82.96% in free radical scavenging activity, other selected plant extracts exhibited moderate antioxidant activities. Among them, the plant extract of Heliotropium indicum (Leaves) showed the best activity in antioxidant activity. Therefore, the selected plant extracts can lead to discovery of natural antioxidant agent.