Today, synthetic dyes have been widely used in comparison to natural dyes because of their cheapness, wide range of bright shades with considerably improved color fastness properties. Moreover, basic dyes are a group of water-soluble dyes which are employed in leather, paper preparing, printing and textile fibers dyeing. This group of dyes among commercial dyes are selected as inexpensive and accessible synthetic dyes, when the brightness and strength of color is necessary. Some of them also have biological activity and antibacterial properties. These colors are used for dyeing of wool, silk, and modified acrylics. Due to their excellent properties, such as brightness and color strength, it should be search the strategies to make them suitable for dyeing of cotton, which is one of the most important cellulosic fibers in the world, and it dedicates about 48% of global consumption due to its physical and chemical properties. Because these dyes have very low affinity to cotton fibers. The purpose of this study was to investigate the adsorption and fastness properties of basic dyes on cellulosic fibers (cotton) by synthetic tannins and natural tannin with potassium antimony tartrate and studying the anti-bacterial properties of dyed samples. In order to achieve this goal for pretreatment of cotton and create anions on surface of it, bleached cotton fabric was treated by different percentages of natural tannin and potassium antimony tartrate in two steps or by syntann in one step. Then, three dyes included in Methylene Blue, Basic Magenta and Basic Orange 2 were selected according to their proper structure for dyeing of the samples and the dyeing process was performed. Then, the adsorption properties of the treated dyed fabrics were investigated by the measurement of adsorption method and it was observed that increasing the amount of tannic acid with tartar emetic or using a certain amount of syntann, increased the amount of absorbed dye by the samples. In the following, the fastness properties of the samples investigated, such as the wash fastness by measuring the amount of the residual dye on dye bath and the light fastness according standard methods. Results showed improvement of wash and color fastness. Also, for the assessment of antibacterial activity, treated and untreated dyed samples were checked out by Disk diffusion susceptibility test, which results representative antibacterial activity of the treated and untreated dyed samples. Keywords: Basic dyes- Cellulose fibers- Cotton- Natural Tannin- Syntann-Potassium Antimony tartrate-Antibacterial properties- Wash and color fastness