Based on the survey data of the China Family Panel Studies (CFPS) and county-level data from the Chinese Population Census in 2010, this paper analyses the impact of gender imbalance on the marriage rate and metal health among marriageable populations. The results show that the rise in gender imbalance significantly reduces the marriage rate among marriageable populations, with males and rural residents being the most affected. The decreased marriage rate due to gender imbalance significantly increases the likelihood of unmarried individuals experiencing depressive emotions. The negative impact of being unmarried on mental health primarily occurs within the older unmarried population, low-income population and rural residents.