Escherichia coli O157:H7 (E.coli O157:H7), is an extremely infectious and potentially fatal water and food-borne pathogen, responsible for numerous hospitalisations and deaths all over the world. Herein we reported the development of simple and label-free electrochemical aptasensor based on single wall carbon nanotube (SWCNT) modified screen printed electrode (SPE) to detect E.coli O157:H7 bacteria. The electrochemical probe of methylene blue (MB) was used to investigate the interactions between aptamer and E.coli O157:H7. The resulting MB/Apt/SWNT/SPE layer exhibited good current response to detect E.coli O157:H7. The aptasensor detect E.coli O157:H7 in the concentration range of 1.7×10 1 - 1.1×10 7 CFU mL -1 and limit of quantification of 1.7×10 1 CFU mL -1 . The proposed aptasensor is rapid, convenient and low-cost for effective sensing of E.coli O157:H7 with high selectivity over interference bacteria. The suitability of the aptasensor for real sample measurements was investigated by recovery studies in tap water sample.