In order to assess the cities' human settlement, this paper proposes a new method according to the elements of niche suitability by the following: (1) the author selects meticulously 25 leading indicators what can reflect the best coupling between the reality niche and the best approximate niche; (2) the author sets up a new quantitative model of multiplies indices using niche suitability on assessing the cities' human settlements. By the way, the indices those the author uses to set up the model are form the economical, social and environmental niche respectively. The new method and the model are used to assessing the Heng Yang City of Hu Nan Province in China in order to take an example for its effect. With the help of the SuperMap-GIS software in his experiment, the author acquires a thematic map of Heng Yang Cities' human settlement, the results of this experiment display that this method and its model are very practicable for assessing a cities' inner human settlement. By the results of this paper, the author expresses his viewpoints for promotion the cities' human settlement that this paper does a research.