This paper analyzes the impact of the interaction between foreign direct investment and human capital on regional economic development. Based on panel data from 16 prefecturelevel cities in Shandong Province from 1990 to 2023, an extended model based on the Cobb-Douglas production function is constructed, introducing the interaction variable between foreign direct investment and human capital to analyze its impact on regional economic development. In this panel regression model, regional economic development is measured by GDP per capita, capital is represented by total fixed asset investment, labor force is the number of employed persons at the end of the year, and human capital is measured as the proportion of students with secondary education and higher to the total population. To further compare the phased characteristics of the interaction between foreign direct investment and human capital, this paper divides the analysis period into three periods: 1990-2023, 1990-2000, and 2001-2023, with China's accession to the World Trade Organization in 2001 as the boundary. Furthermore, regression analyses are conducted on three indicators: human capital at the middle education level, human capital at the high education level, and comprehensive human capital. The empirical results of this paper demonstrate that, first, the interaction between foreign direct investment and human capital exhibits a significant positive effect across all model settings, indicating that this interaction can effectively promote regional economic development. Second, phased results indicate that the interaction between foreign direct investment and human capital was more pronounced between 1990 and 2000. After 2001, despite the overall expansion of foreign direct investment, its interaction with human capital weakened, highlighting the importance of matching human capital structure with foreign direct investment quality. Third, comparing human capital education levels, the interaction between human capital with higher education and foreign direct investment has a stronger impact on regional economic development than that between human capital with middle education, indicating that human capital with higher education plays a more critical role in translating foreign direct investment effects into regional development. In summary, there is a significant complementary relationship between foreign direct investment and human capital, and their deep integration is a key path to enhancing regional economic development. Therefore, while promoting foreign direct investment inflows, regional development policies should also increase investment in human capital, particularly higher education resources, to enhance foreign direct investment absorption capacity and achieve regional economic development.