Abstract: The wellbore blockage caused by hydrate coalescence and deposition is a common safety hazard in gas well testing. The prediction on hydrate formation and deposition laws is conductive to control accident risk and reduce production loss. This paper analyzes the formation and migration of hydrate particles at the tube center and inner wall, respectively. Through introducing the droplet deposition ratio and conversion ratio, a new hydrate deposition prediction model suitable for annular mist flow has been established on the basis of mechanism analysis; it has been verified by experiment simulating the actual reaction under field conditions. The theoretical and experimental values show the same trend with an average deviation of 4.9%, thus validating the reliability of the model. Taking a deepwater well as a case, the hydrate deposition laws at different positions have been studied by numerical simulation. The calculation results indicate that the hydrate deposition and blockage process can be divided into four stages, in which the initial deposition stage and the critical deposition stage account for shorter time, while the deposition metastable growth stage and the deposition rapid growth stage account for longer time. Hydrate blockage mainly occurs in the upper part of wellbore, especially the area near the wellhead. With the increase of depth, the hydrate deposition rate and deposition layer thickness gradually decrease, and the decreasing range increases gradually, reducing the wellbore blockage risk.