Remote sensing drought monitoring model is an important research realm in irrigation and water conservation. From a supposition that the spectral characteristic of bare soil meets linear distribution(Zhan,2005; Abuduwasit,2004) in the NIR(Near Infrared)a2Red reflectance spectral in feature space, a simple and effective remote sensing model has been used to monitor drought which was validated in Ningxia Huia2nation Autonomous region and achieved better results. In order to verify feasibility of PDI(perpendicular drought index) under the dense vegetation cover condition, Hubei Zhanghe Irrigation System was selected as the research area. PDI was calculated with ETM + data, and 2-5 cm soil moisture observation result was used in comparison with PDI. Result shows that 2-5 cm ina2situ observation and PDI calculation display basically the same trend and they are consistent with the field measured drought indices. To sum up, PDI can reflect the land cover and watera2heat combination. PDI has many advantages such as simplicity, practicality, easya2toa2useage, versatility and universality. And it is suitable to monitor regional drought under complex underlying surface conditions.