Droplet freezing phenomenon widely exists in many fields, including aerospace, power production, and cryopreservation, etc. Considering the effects of supercooling, gravity and volume expansion, a theoretical model of droplet freezing is developed. A good agreement is found between the predicted results of freezing front radius and height and experiments for both hydrophilic and hydrophobic surfaces. The developed model also shows good performance in predicting freezing times. The average prediction deviation is 7.63%, and more than 93% simulation results show the deviation within ±15%. Gravity has a more obvious influence on final freezing times with the increase of cold plate temperature, contact angle, and droplet volume. For the droplet freezing process under various contact angles and cold plate temperatures, the fastest average temperature change rates inside water droplet are -2.48 °C/s and -1.72 °C/s, respectively. This study is beneficial for the better understanding of the