Most countries have experienced land urbanization, which is indispensable for financial support, especially for their financing function achievement through land appreciation and other channels in the urbanization process. By using 34 provincial capital (sub-provinces) cities in China as the sample, this paper studies the impact of finance on land urbanization construction based on the panel data from 2003 to 2018 under a differential GMM method; besides, the causes of excessive financial support and results generated on different regions are reported. Moreover, a moderate range of financial support for land urbanization is found under the influence of land finance. We obtain the following results: first, there is excessive financial support for land urbanization with regional differences exhibited; for instance, the eastern and central regions have an excessive financial support but the western region does not. Second, land urbanization with an excessive financial support correlates with financial efficiency, while the relatively large financial efficiency leads to the waste of a large number of financial resources. Third, financial support has a single and significant threshold effect on land urbanization construction, and finance has a promoting effect when land finance is less than the threshold value; otherwise, it has an inhibiting effect.