Abstract： Objective To introduce and evaluate the dosimetric characteristics of a GyroKnife cobalt-60 system for radiosurgery.Methods 0.015 cm3 and 0.600 cm3 ionization chamber,EDR2 film and semiconductor dosimeter were used to measure the dose rate of center point for the four collimators.The diameter of the four collimators were 5 mm,12 mm,30 mm and 50 mm,respectively.0.015 cm3 ionization chamber was used to test the dose-time linear relationship and dose stability.0.015 cm3 ionization chamber and semiconductor was used to measure the dose error of phantom between treatment planning system (TPS)calculation and measurement.The film was used to measure the error of TPS calculation isodose lines width.Results The results from the four measurement methods have no significant difference for the collimator 50 mm.But for collimator 5 mm great discrepancy appeared.The error between calculation by TPS and the measurement by semiconductor was biggest and the value was 4.8％.Most of the error was within 3.0％.The error of the 50％ isodose line along x-axis was biggest and the value was 4.9 mm,others are all within 2.0 mm.Conclusion The dosimetric character of this system is suitable for stereotactic radiotherapy.