The invention discloses a fault-tolerant deflection routing method and device for a bufferless network-on-chip. The method comprises the following steps of: (1) connecting adjacent routers by configurable bidirectional transmission links; (2) coding before sending a data packet, decoding after receiving the data packet, and entering next step when decoding occurs appointed error; (3) pausing the error chain circuit, detecting the chain circuit, if error does not exist during detection, restoring the chain circuit, otherwise, marking the chain circuit to be faulty; and (4) allocating the transmission direction of the chain circuit with unidirectional fault according to the receiving and sending conditions at two ends of the normal chain circuit. The device comprises routers and a direction dispenser for controlling the transmission direction of the chain circuit between the adjacent routers, wherein each router comprises a computing unit, an exchange dispenser, a cross bar switch, a packet updating unit, multiple registers, a testing control unit and multiple direction-allocable transmission control units which are corresponding to the registers. The method and device have the advantages of good fault tolerance, high chain circuit utilization rate and small area expense.