The paper presents a novel fault-tolerant circuit design using a time-redundancy method for a serial-parallel multiplier, which is useful in DSP applications with serial data transmission. It utilises the RECO (REcomputing with Circularly shifted Operands) technique to detect errors concurrently. A simple OR-gate based circuit is used as the location table to identify faulty bit-slice pairs. The reconfiguration technique is then introduced to bypass the potential faulty bit-slices. This design can have the maximum detectable error region ( n/2 bits), without appending extra computing elements. The latency from error detection to location is only about two clock cycles, i.e. almost real-time detecting can be achieved. Pipe-lined timing for two computations is illustrated. The analyses of performance and complexity are described. The results show that this is an efficient design methodology for fault-tolerant multiplication with serial data.