Agricultural transformation is a transition process of agriculture from the low development stage to the high development stage. Identifying the agricultural transformation stage and analyzing the evolution of agricultural development types based on Total Factor Productivity (TFP) are of great significance for the rational formulation of agricultural development policies. Based on the total factor productivity analysis framework, the DEA-Malmquist index model was used to measure the agricultural TFP of the 87 counties in Gansu Province from 1988 to 2017. The cumulative anomaly method was used to help identify agricultural transformation stages. Agricultural development types of counties in different stages and their evolution process were analyzed. Results show that (1) the agricultural transformation of Gansu Province can be divided into three stages: Traditional agriculture in 1988–1998; low-capacity technology agriculture in 1999–2011; and high-capacity technology agriculture in 2012–2017. (2) From 1988 to 2017, the agricultural TFP showed periodic U-shaped fluctuations, and the areas with high TFP value expanded from the central region to the western region and then to the entire region of the province. (3) Gansu Province presented a significant spatiotemporal variation of agricultural development types. From 1988 to 1998, type-I (low technological efficiency and slow technological progress) and type-VI (high technological efficiency and fast technological progress) agricultural development was mainly observed, and these two kinds of counties accounted for 55.17% of all evaluation units. From 1999 to 2011, the number of counties with type-I agricultural development increased significantly, reaching 35, followed by the number of counties with type IV (low technological efficiency) agricultural development, reaching 18. They together accounted for 60.92% of all evaluation units. From 2012 to 2017, the number of counties with type-IV and type-VI agricultural development was the largest, reaching 29 and 25, respectively. They together accounted for 62.07% of all evaluation units. (4) Types of agricultural development frequently change—from 1988 to 2017, the influencing factors of agricultural development had undergone a transition from both technological efficiency and technological improvement to technological efficiency or technological improvement alone.