Abstract: The current studies on the fault characteristics of inverter-based new energy sources all consider that the voltage outer ring is blocked immediately after faults, ignoring the influences of the switching delay of low-voltage ride-through(LVRT) control and the voltage dip detection, thus there is a certain error with the actual current waveform. To address this problem, the mechanism of the voltage dip amplitude detection module leading to the LVRT control delay input is first analyzed. Then based on the voltage transient change process, the whole process of fault current is clearly divided into four stages. This paper focuses on the second stage of the transient current reference value change, and based on the idea of "interval segmentation", the fault current is linearized in segments; finally, a fault transient current analytical calculation model is established, which considers the influences of the control switching delay and voltage dip detection. The waveforms of the proposed fault current analytical calculation basically match with the simulation waveforms of MATLAB/Simulink, which verifies the accuracy and validity of the proposed fault current analytical calculation model, and provides a reference for the subsequent research on the adaptability of relay protection and the new principle of the inverter-type new energy grid-connected system.