Abstract: This paper deals with seven mathematical models within the current COVID-19 pandemic situations. We developed a number of mathematical models which are compartment solutions of nonlinear differential equations. These models are useful for research scholars, faculty members and academicians in the area of mathematical biology. Also, we study these models and parameter estimation from real-world problem (data of COVID-19 in World Health Organization (WHO)). The researchers discussed to analyze the possible solutions of each model in the general discussion section. The researchers recommended that at the end of the year 2020, there will be a reduction on the spread and an increased recovery rate of COVID-19. These situations are fully changed and return to the normal life very soon. In this paper to the researchers discuss the simple SIR model compared to real-life data for COVID-19 pandemic in Tamilnadu by district wise. This model helps to predict the future calculations of Susceptible, Infections, and Removed people from the total population and reproduction number R0 . The researchers conclude that the infection rate is increased for the next two months (September and October, 2020), and death rate percentage is also possible to decrease from the number of total populations. Also the researchers recommend the continuous lockdown for these two months and for all people to follow the instruction given by the Tamilnadu Government.