Abstract: Population parameter estimation and spatial distribution pattern are the main issues in animal ecology and conservation biology. In recent decades, camera trap as a noninvasive technique in field survey has been widely used in wildlife ecology and conservation research, and showed its great superiority under the conditions of traditional survey methods difficult to achieve. The animal presence data collected by camera trap can provide extremely valuable quantitative information on wildlife populations. In this review, the operational principles of camera trap were introduced to provide an intuitive understanding of this technique, and then, the applications of this technique in two main fields of population ecology, i.e., population density and abundance estimation and spatial occupancy estimation for the species with or without natural unique individual markings, were discussed, with special attention to the logic of development, assumptions, limits in application, challenges, and future directions of model development. Finally, the important aspects which should be kept in mind when using camera trap in estimating wildlife population parameters as well as the potential capacities of camera trap in the researches of population dynamics and biodiversity, were comprehensively analyzed.