The population of India at 0:00 hour of 1st March 2001, stood 1,027,015,247 comprising 531,277,078 males and 495,738,169 females. As widely believed and expected, India became the second country in the world after China to cross officially one billionth mark. Changes in sex composition largely reflect the underlying socio-economic and cultural pattern of a society in different ways. The sex ratio of Indian population has always been a topical interest for the demographers, social scientists, women’s groups, research scholars and various planners and policy makers. This paper is an attempt to study the ratio percentage of female population in India over the male population. This study also focus on some related indicators and parameters because of which it reflects. It also pin-out the change in world sex ratio.