As heavy-haul railway plays an increasingly important role in cargo transportation, the security of their broadband mobile communication networks becomes more and more critical. Aiming at the limitations of traditional network security testing methods such as restricted evaluation scope and large resource consumption, cyber range technology is innovatively introduced to conduct the security evaluation of heavy-haul railway broadband mobile communication network. Seven security assessment indicators for the broadband mobile communication network of heavy-haul railways have been determined, including data link layer testing, interface testing, Operation, Administration, and Maintenance(OAM) system security testing, network, configuration management testing, performance pressure testing, vulnerability scanning and penetration testing, and security operation and maintenance monitoring testing. The specific testing contents of each assessment indicator are elaborated. The cyber range is employed to simulate the real environment, and Distributed Denial of Service(DDoS) attacks, malware attacks, authentication attacks and network delay attacks are selected as the four typical scenarios that are more common and representative in actual operation for testing. Based on the four attack and defense scenarios, the data of Central Processing Unit(CPU) utilization, memory utilization, bandwidth, latency, jitter and packet loss rate changes of each network element and link under attack are obtained. Finally, the network risk assessment is carried out using the hierarchical analysis method, and the results can be used as a reference for the security assessment of heavy-duty railroad networks.