Our study aimed to determine the effect on barley (Hordeum vulgare L.) of adding potassium polyacrylate to a sandy soil under normal watering condition and drought. We focused on morphological and physiological characteristics of barley and its rhizosphere bacterial community structure using Illumina Miseq sequencing. It was found that under normal watering condition (70% of soil water holding capacity (WHC)), the soil water retention increased with the SAP addition to the soil. Barley plant height and weight, leaf relative water content and protein content decreased under drought (35% of soil WHC), the addition of SAP eliminated the negative effect of drought on plants, the proline content was reduced from 2.71 μg g−1 leave dry weight with stressed plants to 0.99 μg g−1 with only 0.2% of SAP. The barley rhizophere bacterial community was affected by drought. Changes in relative abundance were noticed at both phyla and OTU level. The SAP addition (0.8%) shifted the barley rhizophere bacterial community to become in part more similar to that of the normal watering condition. Also, we found that the SAP addition had a side effect itself on the barley rhizosphere bacterial community other than its capacity of water holding.