BACKGROUND: Halcyon has an enclosed, ring-mounted gantry and a 6 MV flattening filter free (FFF) beam. This beam is used for both treatment and imaging for Halcyon version B. METHODS: The dosimetric stability performance of the Varian HALCYON has been studied 6 times in one year since its installation. All dosimetric data obtained by own Halcyon software by Machine performance check (MPC) method. RESULTS: The average value of all six sets of dosimetric data show well agreement within manufacture’s Thresholds. Which means Halcyon can deliver accurate and precise radiation to particular target area as per requirement. CONCLUSION: Our study concludes that Halcyon is a good compact linear accelerator which can be easily used for modern radiotherapy treatment and patient imaging purposes.