Experimental observations together with theoretical analysis were conducted to investigate the break phenomenon and the corresponding mechanisms of self-pulsation for a liquid-centered swirl coaxial injector with recess number of RN=1. Instantaneous spray images were obtained based on background light imaging technology with a high-speed camera. By dynamic analysis of the flow process of the liquid sheet in the recess chamber, a 1D self-pulsation theoretical model was established, and the self-sustaining mechanisms of self-pulsation were analyzed in depth. The results show that the increase of the momentum flux ratio will lead to the occurrence of the break phenomenon of self-pulsation for the injector with a larger recess length, and the frequency and intensity of self-pulsation before and after the break phenomenon differ significantly. The flow dynamics in the recess chamber sequentially transform from a periodic expansion-dominated flow to a stable flow, and then develop to a periodic contraction-dominated flow during the break process of self-pulsation. With the occurrence of self-pulsation before the break phenomenon, the liquid sheet has little effect on the pressure disturbance in the recess chamber. In contrast, with the occurrence of self-pulsation after the break phenomenon, the pressure disturbance is obviously affected by the liquid sheet. Based on the theoretical analysis model of self-pulsation, the self-pulsation frequency can be predicted. Furthermore, the self-sustaining mechanism of self-pulsation before and after the break phenomenon is preliminarily confirmed. The energy transfer between the gas-and liquid-phase is an important factor for maintaining the self-pulsation process.