The invention relates to a steel wire rope tensioning mechanism for a quayside container bridge type crane trolley. The steel wire rope tensioning mechanism comprises a tension driving mechanism, a traction drum, a tensioning drum, a tensioning fixed pulley block, a sensor and rope pressing plates, wherein the tension driving mechanism comprises an encoder, a motor and a planet gearbox; the tension driving mechanism is positioned on the trolley; the encoder is arranged at one end of the motor; the tension driving mechanism is arranged on the tensioning drum; the tensioning drum is arranged on the trolley through a bearing block; the tensioning fixed pulley block is fixed on the trolley; the sensor is arranged on a shaft of a first fixed pulley block at the head of a front girder; the rope pressing plates are fixed at two ends of the tensioning drum. The steel wire rope tensioning mechanism has the advantages of energy conservation, environmental protection, high reliability, easiness for operation, compact structure and small occupied space; the effect of accurate control can be realized; the tensioning degree of the steel wire rope can be realized in a wide range; the steel wire tensioning mechanism is easy for maintenance, investigation and repair.