With the burgeoning population and growing industrialization, there is a negative correlation found with the availability of agricultural land and a positive correlation found with the demand for food. Climate change further have its negative impact on food production and aggravate the need of food demand. Crop simulation models are quite useful to sustain the production system forecasting the outcomes to a given situation and considering these obstacles for farmers, private agencies and policy makers to a greater extent for the decision making. Crop simulation is being used for characterizing and predicting the crop growth and yield under different climatic conditions and crop management options. Use of Crop model is an innovative and efficient technology as a decision-making tool for the agricultural production system. Crop simulation models will be of greater acceptance if they have certain characteristics i.e. robust, easily accessible and easy to use. In this chapter there is an effort to make the reader understand the importance of crop modelling as a tool providing some important crop models in brief.