Gravitational water vortex power plant is an emerging technology among various micro hydro-power plants because of its low head, cost-effectiveness, environmentally friendly and minimal installation and setup time. In the present study, the performance of single-stage gravitational water vortex turbine assembled in a conical basin with curved blade has been analyzed at different head and flow rate to investigate the performance parameters such as vortex formation, vortex height and rotational speed. In addition to that, the influence of vortex formation, vortex height and vortex shape on rotational speed is also investigated. A two input factors, i.e. water head and flow rate, and each having five-level has been selected in a present study. The results showed that at median head 0.70 m and flow rate 0.004 m³/s, the maximum rotational speed 172 rpm and vortex height 0.59 m, respectively, with strong and fully developed air core is achieved which results in high output power and efficiency. However, the water disturbance, weak shape vortex formation and decrease in the vortex height and rotational speed occurred at a minimum and maximum inlet head of 0.6 m and 0.8 m and flow rates of 0.002 m³/s and 0.006m³/s flow rates, respectively, which results in a decrease in the overall performance of Gravitational water vortex turbine. Further, the vortex formation, vortex height and vortex shape strongly influence the rotational speed. Overall, 0.7 m head and 0.004 m³/s developed a strong vortex with a rotational speed of 172 rpm and vortex height of 0.59 m. Furthermore, Analysis of Variance was performed to investigate the percentage contribution and significance of each input parameter on response.