The main objective of this paper is to introduce the implementation of Perpendicular Drought Index（PDI）

a simple

effective drought monitoring tool

in integrated remote sensing supporting system（IRSSS） for parameter retrieval and drought estimation.The quantitative remote sensing models are changing and various and the remote sensing data formats are complex and diverse.The research group used component oriented programming thoughts to solve these problems

making this system extendable in data source and models.The system could deal with various familiar formats of RS image.According to the COM rule

the IRSSS developed a particular interface in order to guarantee the users add new function module or file I/O driver by themselves.This paper introduces the implementation of PDI using C++ program language.There are four steps designed to complete the task.The general process and purpose of every step is explained and especially the method of finding soil point and memory management are introduced as the key technology.Our research group has implemented the drought-monitoring function based on the basis of the IRSSS system.Furthermore

according to the observation data of Ningxia the research group generated many results of various Drought Indices.The paper also presents the results of evaluated drought situation of Ningxia Huizu Autonomous Region of China that indicates the accordance with regional hydro-environmental data.