Addressing the shortcomings of traditional multi-core fiber beam splitters and multi-core fiber connections, such as dif-ficulties in disassembly and the need for additional test beam splitters in testing solutions, a four-core fiber channel beam splitter is prepared using a double-clad fiber bundle tapering method. To facilitate device testing and connection, LC/PC-type active connectors are prepared at the ends of the single-mode fiber and the four-core fiber, thus forming a single modular four-core fiber channel beam splitter. Meanwhile, a mirror-based testing method is proposed for this modular device. This testing method requires only one LC/PC active connector-type mirror to easily complete the testing of the device's insertion loss and inter-core crosstalk. The test results indicate that the prepared four-core fiber channel beam splitter exhibits excellent performance, with a maximum insertion loss of 0.84 dB and a maximum inter-core crosstalk of -46.32 dB.