Abstract: In order to establish the bond-slip (?-s) constitutive relationship between ash concrete and crescent reinforce bars, straw ash was mixed into concrete as equivalent replacement of 5%, 10% and 15% of cement amount to make bond specimens of different strength grade, C20, C30 and C40. The ?1-s1 curves of ash concrete and crescent reinforced bar were obtained through the test of central pull-out. Based on ?1-s1 curves, the constitutive models of ash concrete and three kinds of crescent reinforce bar with different diameters (12, 16, 20 mm) were established. In addition, the change of ?1-s1 curve of ash concrete under different ash content was explained in according to electron microscopy scanning. Finally, spring2 in ABAQUS was used to simulate the central pull-out test. The results showed that both compressive strength and tensile strength of concrete cube decrease with the increase of ash content. However, comparing with high-strength concrete, low-strength concrete reflects its advantages better because of ash incorporation. Splitting failure and pull-out failure are the main bond failure modes between ash concrete and crescent steel bar. And splitting-pull-out failure only occurs in those bond specimens with 15% ash content, C20 concrete design strength grade and 12 mm diameter steel bar. When the ash content is 5%, the micro-structure of concrete is continuous and compact, and the bonding performance is the best. When the ash content increases to 15%, compared with the control concrete, the micro-morphology of concrete changes to loose and porous from continuous and compact, which leads to 52% reduction of concrete splitting tensile strength. The bonding performance between ash concrete and crescent steel bar is correspondingly weakened, and the shape parameters in ?-s constitutive model is also changed with the change of mixing amount of ash. When the ash content is 5%, the ?-s curve coincides with the normal concrete, compared with the control concrete, the ultimate bond strength of ash concrete only decreases by 6%. With the increase of ash content to 10% and 15%, the bond performance between ash concrete and steel bar is obviously weakened. Compared with plain concrete, the ultimate bond strength of ash concrete with 10% and 15% ash content decreases by 17% and 32% respectively. For bond specimens with diameters of 16 and 20 mm, splitting failure of concrete occurs prematurely, so that ?-s curve only shows an ascending section. The bond performance law of the two types of steel bar is similar to that of steel bar with diameter of 12mm, that is, with 5% ash content concrete performs the best bond strength. And the bond performance becomes worse with the increase of ash content. Finally, the ?-s constitutive model of this study was input into spring 2 unit of ABAQUS software to verify the accuracy of the model, the central pulling test was successfully simulated based on ABAQUS software. The results showed that the test ?-s curve closely fits the ABAQUS simulation curve, and the fitting determination coefficient is 0.94, which proves the validity of ?-s model of this study. Comparing with Harajli ?-s model, the fitting variance of the ?-s model in this study is reduced by 50% from 0.002 to 0.001, and its fitting stability is better than that of Harajli ?-s constitutive model.