We conducted this research to explore the possible factors shaping son preference, with a view to understanding the persistently high male/female sex ratio. Using data from the Chinese General Social Survey (CGSS) and the Population Census of China, we find a significant impact of regional sex ratio on people's preferences for the sex of their future children. Specifically, the extent of son preference decreases with the increase in the male/female sex imbalance in the local area. We also find that sex imbalance has a positive impact on a wide range of outcomes that capture the pressure on males to enter marriage markets, such as regional housing prices, the number of houses owned, and family economic status. This result is consistent with the view that greater sex imbalance exerts larger pressure on men in the marriage market, leading to changes in son preference. Omitted variable bias is addressed by using climate changes in the month preceding the fertilization period as an instrument for sex ratio. Instrumental sex ratio negatively impacts son preference, offering strong support for our hypothesis.