This　paper　describes　a　fieldbus　of　which　the　physical　layer　using　CAN　(Controller　Area　Network)　transmission　line　and　the　data　link　layer　using　SPI　(Serial　Peripheral　Interface)　interface　protocol.　It　applies　to　the　two-way　information　exchange　between　the　controller　(master)　and　the　sensor/actuator　(slave),　to　build　the　underlying　network　monitoring　system.　The　bus　takes　the　advantage　of　the　electrical　characteristics　of　CAN　transmission　line,　and　the　bus　inherits　its　anti-interference　ability　and　the　advantage　of　long　transmission　distance.　Also,　it　inherits　the　merits　of　SPI　bus　communication　such　as　fast,　easy　to　use　and　low　cost.　Compared　with　the　half　duplex　distributed　network　constructed　by　EIA-485,　the　slave　in　this　bus　is　a　pure　hardware　device,　saving　the　MCU　chip　and　software　programming.　This　paper　presents　a　new　bus　communication　protocols　and　hardware　structure　of　slave　interface　module　and　describes　the　working　principle　of　the　interface　circuit.　Finally,　experimental　data　and　test　results　are　given,　verifying　the　feasibility　and　communication　features　of　this　type　of　bus　and　the　interface　module　design.　©　2015　-　IOS　Press　and　the　authors.