This thesis deals with the Estimation of total solar irradiance from sunspot number. Thus, the present thesis has five chapters. Chapter one deals with background of the study that addresses the research question, purpose, significance, scope (delimitation), limitation and definition of operational terms. In chapter two different literature are reviewed regarding the variables treated from international perspective. It also, provides a comprehensive literature review on the total solar irradiance (TSI), sunspot numbers and the estimation techniques of TSI from different proxies. Moreover, the solar cycle, solar activity and climate change are presented in detail. In chapter three we discussed about design, instrument, procedure and data analysis technique. Chapter four deals with the detail analysis of the research finings and discussions. Finally, chapter five contains the conclusion, and recommendation for further research work.