Time-of-flight measurement is one of the principles of 3D sensation systems. In recent years, with the development of semiconductor technology, time-of-flight measurement systems based on the signal correlation method have developed rapidly in the field of three-dimensional imaging due to its advantages of all solid-state components, high integration and low power consumption. The mathematical principles of correlation time-of-flight measurement techniques were systematically studied, its error sources were analysed, the mathematical models were constructed, and different types of measurement errors were compared. The research results show that light source error, multipath and ambient light interference are the main factors that restrict the measurement accuracy and application range of time-of-flight imaging systems.