Mg-Zn alloys have a large freezing zone, and their susceptibility to hot tearing is high. Investigations on their hot tearing are necessary for both materials science and practical applications. The present work evaluates the susceptibility of hot tearing of Mg-Zn alloy using Clyne and Davies's modelling combined with thermodynamic calculations. In order to compare with the calculated results, the susceptibility of hot tearing was measured using previously developed quantitative experimental method. It is found that the simulation results are in agreement with the experimental results. Both of them show that the curves of the susceptibility of hot tearing versus the content of Zn has a typical 'Λ' shape. With increasing content of Zn, the susceptibility of hot tearing first increases, reaches the maximum at 2-4%Zn and then decreases again. Experimental investigations also demonstrate that the hot tearing susceptibility decreases with increasing initial mould temperature.