Though the Global Navigation Satellite System (GNSS) has become the primary mean to provide high-precision and high-integrity services for many aeronautical applications, GNSS is vulnerable to interference because of its low signal strength. DME/DME as the main reversionary method provides Alternative Positioning, Navigation and Timing (A-PNT) services for use during a GNSS outage. When there is only one pair of DMEs used to aircraft location detection, the distribution of these 2 stations has strict requirements. Considering the geometry limitation of DME/DME, multi-DME with better geometry can be used to increase the accuracy and integrity of positioning. In this paper, we further proposed the integrity monitoring method for A-PNT using barometric measurements aided multi-DMEs. The combination of the barometric altimeter and multi-DME system can make full use of the altitude value provided by the barometer altimeter to improve the geometric performance of the DME stations and the availability of the autonomous integrity monitoring. The test results demonstrate that RNP 1 can be achieved by both methods for most part of Europe, and the using barometric measurements aided multi-DMEs method improves the performance of the autonomous integrity monitoring on both fault detection capability and protection level.