The fertility of urban soil is an important factor for urban forestry and urban greening. There has been no comprehensive evaluation of soil fertility at the city scale upon which to base greening practices in Changchun City. In this study, 197 soil samples from the 0-20 cm layer were collected to determine soil organic matter (SOM), total nitrogen (TN), total phosphorus (TP), total potassium (TK), available nitrogen (AN), available phosphorus (AP), available potassium (AK), pH, and soil bulk density. Variables analyzed with respect to differences in soil fertility were forest types (roadside forest[RF], affiliated forest[AF], landscape forest[LF], and farmland shelterbelt forest[FF]), districts (Chaoyang, Lvyuan, Nanguan, Kuancheng, and Erdao districts), and ring roads (1-4 ring roads and outside 4-ring roads). Classification criteria for soil nutrients in the 2nd National Soil Survey (6-grade evaluation) and a modified Nemorow formula were used to compare soil fertility. Moreover, kriging interpolation was used to map the spatial distribution of soil nutrients and fertility using ArcGIS software. With reference to the 6-grade criteria from the 2nd National Soil Survey, SOM in Changchun was graded as no. 2 (high level) with an average of 34.51 g/kg and most regions had >30 g/kg. TN, AN, and AP were graded no. 3 or higher, with an average of 1.37 g/kg, 133.04 mg/kg and 38.47 mg/kg, respectively. The spatial map revealed that most urban regions had TN 1-1.5 g/kg, AN 90-150 mg/kg and AP 20-40 mg/kg. TK and AK were graded the highest (grade no. 1) averaging 58.7 g/kg and 255.85 mg/kg, respectively, and most regions had 50-60 g/kg and 200-300 mg/kg, respectively, based on the ArcGIS map analysis. TP reached the mid-low level (no. 4 grade), averaging 0.51 g/kg and most regions on the spatial map had 0.4-0.6 g/kg. The pH of the urban forest soil ranged from 5.43 to 8.89, and soil bulk density was in the range of 1.11-1.62 g/cm³. Spatial distribution of the Nemorow comprehensive soil fertility index (F) revealed that most urban regions were within the 1.5-1.8 range, indicating medium soil fertility overall for Changchun City (grade no. 3 in the 4-grade system). In addition, forest type-related differences were mainly found in pH, TN, TP, and TK (P < 0.05), and ring road-related urban-rural gradient differences occurred in pH, SOM, and TP (P < 0.05), whereas administrative district-related differences were found in all studied parameters, except soil bulk density, TK, and AK (P < 0.05). F differences in different forest types followed the sequence LF > AF=FF > RF. In different administrative districts, the sequence was Lvyuan > Chaoyang > Nanguan > Erdao > Kuancheng, whereas for ring road-related F differences it was 1-ring > 3-ring=4-ring > 2-ring > outside 4-ring. Based on these results, some measures to improve the urban soil of Changchun were proposed, such as loosening soil, reducing soil alkalinity, litter compost cycling on-site, N-P fertilizer addition without the addition of K, and N-fixing using trees with low P demand to maintain suitable soil fertility. These soil diagnosis-oriented measures could promote better development of urban forests and green spaces, and our data provided an example of urban soil fertility evaluation for improving soil-based urban vegetation ecological services for resident life.