The COVID-19 outbreak has restricted the freedom of ordinary people, resulting in less activity and more negative emotions. Consequently, we proposed a motor imagery training procedure to intervene in the mental health problems of people with freedom restrictions. We conducted two studies. Study 1 had 176 participants, including 93 in the freely restricted group (Mage=19.66, SD=1.16), and 83 in the non-freely restricted group (Mage=21.4, SD=1.16). The freely restricted group had more negative emotions than the non-freely restricted group. Study 2 had 106 valid participants who were randomly divided into two groups with 48 in the experimental group (Mage=19.46, SD=0.87), who received motor imagery training, and 58 in the control group (Mage=19.41, SD=0.94), who did not receive motor imagery training. The posttest positive emotion scores were significantly higher in the experimental group than in the pretest, while the posttest positive emotion scores were lower in the control group than in the pretest. This result confirms that motor imagery training can effectively promote positive emotions of sequestered individuals during a pandemic. Our study provides a solution to reduce psychological problems, particularly the promotion of positive affect, in personnel with restricted freedom in COVID-19 sequestration, and in other personnel with restricted activities.