Abstract: Mastering the spatiotemporal evolution patterns of rural functions is an important foundation for promoting the modernization of agriculture and rural areas and for building a livable, business-friendly, and beautiful countryside. Taking 38 counties in the two main grain producing areas of the Songnen Plain and Sanjiang Plain in Heilongjiang Province as the research objects, this paper constructed the evaluation index system from the three dimensions of rural production, life, and ecology, analyzed the spatiotemporal evolution of its rural function and its functional positioning, and applied the geodetic detector model to explore the driving factors for the spatiotemporal evolution of the rural functions. Results show that the overall trend of the “Production-Living-Ecology” functions of the rural areas in the counties exhibited a continuous upward trend from 2002 to 2022. Specifically, rural production and life functions have improved significantly, while ecological functions have shown no obvious improvement. According to the evolution characteristics of rural functions, the 38 counties in the two major grain-producing areas are classified into four types: single-function dominant, dual-function coordinated development, multifunction development, and weak comprehensive rural areas. The level of agricultural mechanization is a major driving factor affecting the evolution of rural functions. Most interactions among influencing factors exhibit double-factor enhancement effects, with the strongest interaction occurring between machine-land area and annual precipitation. Based on these findings, this paper provides some differentiated policy recommendations for rural areas with different functional types.