Culture is considered to be a deep-seated factor affecting economic development, among which the economic impact of cultural diversity has attracted considerable attention. At the county level, clans play an important cultural and social role. Although traditional clans in China are influenced by Confucianism, different clans have different cultural inheritance. Genealogy, ancestral precepts and clan rules are the carriers of each clan's ideological inheritance. Different clans are distinguished by surnames, and cultural backgrounds and concepts are quite diverse. This paper will examine the impact of this diversity on the performance of county economic development. This paper collects the data of the Chinese Genealogy published by the Shanghai Library, collates and constructs the number of clan surnames and the diversity index of clan surnames in 1087 counties, and uses the night light brightness data released by the National Oceanic and Atmospheric Administration (NOAA) to measure the economic development performance of counties in China. Empirical results show that the diversity of clan surnames has a significant positive impact on the performance of county economic development, which remains stable in the test. The more diverse the clan surnames are, the better the economic development performance of counties will be.