The steep drop in efficiency seriously affects the output performance of AlGaN-based deep ultraviolet light-emitting diodes (DUV LEDs)， and is also a bottleneck problem for DUV LEDs in recent years. DUV LEDs with conventional electron blocking layer (P-EBL) and Al composition triangular graded P-EBL are investigated numerically in this paper. The distribution characteristics of energy band， electron current， hole concentration， electric field， internal quantum efficiency， output power and spontaneous emission spectrum are investigated.The simulation results show that when 260 mA current is injected， compared with the conventional P-EBL structure， the efficiency drop of the Al composition triangular graded P-EBL structure DUV LED is reduced by 5.85%， which improves the output performance of the DUV LED. Based on the numerical simulation and analysis， these improvements on the device characteristics are attributed to the remarkable improvement of the electron leakage and hole injection efficiency， which results from the higher effective conduction band barrier height for limitting electrons， and the higher kinetic energy for hole transportation in the P-side.