Field experiment was conducted during 2017-18 in sandy loam soil at Instructional Farm, College of Technology and Engineering, Udaipur. Study has been done to evaluate the effect of deficit irrigation and determine the desire irrigation water requirement of quinoa crop using IW/E-Pan. Using these approaches, further study has been done to determine effect of deficit irrigation on grain yield, straw yield, irrigation production efficiency and economic return of quinoa crop. In IW/E-Pan approach, irrigation application was based on different ratios of IW/E-Pan. Irrigation of 60 mm was applied on the basis of IW/E-Pan ratio of 1.0, 0.9, 0.8, 0.7, and 0.6. The maximum grain yield and straw yield as 14.99 and 12.23 q/ha respectively was found by irrigation applied with 0.7 IW/E-Pan ratio. Study also revealed that, the maximum water use efficiency as 177.39, 96.96 and 80.43 kg/ha-cm was recorded in total crop yield, total grain yield and straw yield respectively under the treatment T5 (IW/E-Pan ratio = 0.6). The relation of grain yield and total water applied has been derived and correlation coefficient R2 was found as 0.89 by second degree polynomial relationship, therefore second degree polynomial equation found best suited equation under IW/E-Pan approach.