An information security testing method and an information security testing system of an open radio access network (O-RAN) base station are provided. The information security testing method includes at least the following steps: configuring a processing device to execute a radio resource control (RRC) signaling integrity test process to determine whether or not an RRC signaling sent by a central unit (CU) is integrity protected; and in response to determining that the RRC signaling sent by the CU is integrity protected, configuring the processing device to execute an RRC signaling security test process.