To investigate the relationship between photosynthetic capacity and soil factors of typical plants in the semi-arid zone of the Loess Plateau and to quantitatively study the response of plant photosynthetic characteristics to soil factors, in this study, we used Li-6400 portable photosynthesis meter to measure the photosynthetic capacity of leaves of different life types of plants and fit their CO2 response curves, and we obtained the maximum carboxylation rate (V-cmax), the maximum electron transfer rate (J(max)), mitochondrial respiration rate in light (R-d), triose phosphate use limitation (TPU) and J(max)/V-cmax ratio, etc. We also applied a GAM model to analyze the relationship between photosynthetic characteristics and soil factors. The results showed that: (1) With the increase of intercellular CO2 concentration (C-i), the net photosynthetic rate (P-n) of different life types of plants increased almost linearly, and P-n increased with the increase of C-i at C-i < 500 mu mol/mol, and then the growth rate gradually slowed down; under the condition of the same CO2 concentration, the size of P-n was ranked as herbs > trees > shrubs, and the P-n values of different life types of plants all reached the maximum in May and the minimum in July. (2) The photosynthetic parameters such as V-cmax and J(max) of leaves of trees, shrubs, and herbs were significantly different (P < 0.05), and the V-cmax, J(max), R-d, and TPU were herb > tree > shrub, and J(max) /V-cmax ratio was shrub > herb > tree. (3) Based on the GAM model, we found that the six environmental factors on P-n were in the following order: T-a > PAR > STP > STN > SWC > SOM, and except for SOM, P-n was significantly and non-linearly correlated with the other environmental factors. Conclusions: Herbaceous plants are very competitive in their habitat. The differences in photosynthetic capacity of different types of plants may be related to their leaf structure and composition. T-a, PAR, SWC, and STN are the main factors affecting the magnitude of P-nmax. Therefore, according to the different degrees of influence of the environmental factors on the photosynthetic capacity of the plants, we can provide reasonable measures of replenishment for plant growth in other months and offer a good solution for the cultivation of plants and vegetation growth of plants in semi-arid areas of the Loess Plateau. It can provide a theoretical basis and data support for the cultivation of plants and the improvement of vegetation survival rate in the semi-arid region of the Loess Plateau.