Modulation transfer function (MTF) is an important parameter for image quality evaluation of satellite optical sensors. In-flight MTF measurement is also significant to the application of high resolution satellite remote sensing data and development of future satellite sensors. There are many on-orbit MTF estimation methods such as knife-edge method, pulse method, point source method and periodic target method. All these methods have their own features and achieved a certain degree of results. In order to improve MTF estimation accuracy of different spatial resolution optical satellite sensors, comparison and analysis are carried out in application scope, target deployment, data processing and application effects of different methods by expositing in-flight MTF measurement which is commonly used.