The development of economy and urbanization promotes the transformation of land use both in space and function. Most existing research perspectives focus only on the transformation of space or function, and analysis of the mutual feedback mechanism between space transformation and function transformation is not deep enough. Therefore, this study constructed a diagnostic method for land use space transformation and function transformation and explored the mutual feedback mechanism between space transformation and functional transformation. The purpose is to deepen the research of land system science, provide a new method for diagnosing the space transformation and function transformation of land use, and clarify the driving mechanism of space transformation on function transformation as well as the mutual feedback mechanism of both. The research results showed that: (1) From 1980 to 2000, the space transformation of land use in the Northern Shaanxi Plateau did not happen, but the degree of trade-off between functions increased, resulting in the occurrence of unsustainable function transformation; the Guanzhong Plain showed a sustainable space transformation during the study period, but the land use functions did not transform; the function transformation and space transformation of the Qinba Mountain area happened in the same direction, and both tended to be sustainable; (2) From 2000 to 2018, the space transformation and function transformation of the Northern Shaanxi Plateau were in opposite directions; the land use space in the Qinba Mountain area was in a state of fluctuation and had not undergone transition, but the land use functions were in an unsustainable transition state; and (3) The function transformation in Shaanxi Province was deeply affected by factors at the policy and cultural levels and the strengthening of its own anti-interference ability, resulting in different performances of space transformation in different regions in different periods. Therefore, Shaanxi Province should rationally plan land resources, coordinate the relationship between space transformation and function transformation, and offer positive feedback to function transformation through sustainable space transformation. Meanwhile, it is necessary to prudently determine the regional land use model according to regional differences.