The ratio of the number of injured people to fatalities in earthquakes not only reflects the vulnerability of countries or regions in earthquakes, but also is useful for the estimation of injured people, which is of great importance for emergency rescue. The ratio of injured people to fatalities is often represented by a fixed number in existing research, but disparity of these ratios from different earthquakes is clear. By analyzing the correlation between the number of injured people in earthquakes and fatalities, this study establishes regression models using the injured people and fatalities data in China since 1989. The models are tested and used to predict the ratio of injured people to fatalities in earthquakes with different levels of fatalities. The results show that: (1) There is a significant positive correlation between the number of injured people and fatalities in earthquakes, not only for China, but also worldwide. (2) Power function can better reflect the relationship between the number of injured people in earthquakes and fatalities in China. Large fatalities are always accompanied by low ratio of injured people to fatalities. The models and the calculated ratio of injured people to fatalities in this article provide an alternative method to estimate the number of injured people in earthquakes.