Since future universal access transceiver 2 （UAT2） mode automatic dependent surveillance-broadcast （ADS-B） devices for low-altitude aircraft surveillance would face overlapping messages in high-traffic scenarios， this study combines probabilistic algorithms such as Poisson process and the binomial distribution with the features of the UAT2 data link transmission and reception process to tackle this potential issue. A relationship model is established to quantify the relations between the success rate of ADS-B receiving equipment receiving a single message and various influencing factors. This model reveals that the surveillance capacity of the ADS-B receiving equipment is jointly determined by the channel bit error rate and the sampling rate under both ideal operational conditions and conditions involving message overlapping. Simulation results indicate that when the minimum message reception success rate of 70% is set as the goal， the surveillance capacity can reach 199 s^-1 with a channel bit error rate of 10^-2， and 256 s^-1 with a bit error rate of 10^-3. The simulation results closely fit the model curves， validating the reasonableness of the proposed quantification assessment model for the surveillance capacity of UAT2 data link ADS-B receiving equipment.