This paper provides analysis and test results on detection performance of Transmitter Identification (TxID) in Advanced Television Systems Committee (ATSC) 3.0 system. In the next generation of the terrestrial broadcasting system based on ATSC 3.0, it is likely that single frequency network (SFN) is widely deployed. In SFN environment, the detection performance of TxID can be degraded depending on the number of transmitters and its relative reception power from multiple transmitters. In this paper, in terms of TxID detection performance, the impact of multiple transmission signals is analyzed through the computer simulation, laboratory test, and field test.