In response to the problems that oyster seedling string is produced with high labor intensity, high labor cost and low work efficiency, a kind of automatic production device for knot rope oyster seedling string is developed. The device takes the nylon rope, PVC belt and rust-proof magnesium alloy wire as processing raw materials and PLC as the core to control stepping motors and cylinders, so as to combine the processes including punching, wearing rope, wire delivery, wire cutting, knotting, cutting and folding together in one working process. Through the man-machine interface, it can realize real-time working status monitoring, real-time modification of process parameters, real-time data base and alarm, etc. The prototype test finds that the average success rate of automatic production of seedling string is over 96.55 %，and the device runs stably and reliably and has strong practicability, which reduces labor intensity and labor cost and improves production efficiency. The design may provide reference for the development and application of the automatic production device of the fixed shellfish sampler.