The main objectives of this study were, to investigate the influence of different vacuum levels (VL), pulsation ratio (PR), claw size (CS) and connection of Duovac unit on characteristics of milking machine, in order to provide preliminary information for future trials on milk flow rate and milking time of Friesian cows. The present study was carried out at Sakha Animal Production Research Station, Kafr El-Sheikh Governorate. Results revealed that machine milking yield (MMY) increased (P<0.05) from 8.7 kg at VL of 48 kp < sub>a to 9.0 and 9.05 kg at VL of 50 and 52 kp < sub>a, respectively. Total milk yield (TMY) increased (P<0.05) as the VL increased from 48 (8.9 kg) up to 52 Kp < sub>a (9.8 kg). Stimulation time (ST) was shorter (P<0.05) at 50 Kp < sub>a than at 52 Kp < sub>a (10.4 vs. 10.9 sec). Machine milking time (MMT) decreased (P<0.05) from 4.4 to 3.9 min by increasing VL from 48 to 50 kp < sub>a and to 3.5 min at 52 kp < sub>a. Stripping milk yield (SMT) only increased (P<0.05) from 0.6 min at 50 kp < sub>a to 0.9 min at 52 kp < sub>a. Total milking time (TMT) decreased (P< 0.05) from 4.9 min at 48 kp < sub>a to 4.6 and 4.4 min at 50 and 52 kp < sub>a, respectively. Milk flow rate (MFR) increased (P<0.05) from 2.0 to 2.3 kg/min at 50 kp < sub>a and to 2.8 kg/min at 52 kp < sub>a.Stripping milk yield (SMY) relative to TMY was higher (2.7%, P<0.05) for 48 Kp < sub>a than 50 and 52 Kp < sub>a (2.3 and 2.4%). Values of MMY decreased (P<0.05) only by changing PR from 65:35 up to 70:30 (8.7 vs. 9.2 kg). SMY decreased (P<0.05) by 33% only with changing PR from 60:40 to 65:35. TMY decreased (P<0.05) from 9.7 to 9.4 kg by changing PR from 60:40 to 65:35. However, changing PR from 65:35 to 70:30 reduced (P<0.05) TMY from 9.4 to 8.9 kg. ST decreased (P<0.05) from 11.3 to 10.5 sec only by changing pulsation ratio from 60:40 to 65:35. TMT was longer (1.9 vs. 4.6 min, P<0.05) by changing PR from 60:40 to 65:35 and from 65:35 to 70:30 (4.6 vs. 4.5 min, P<0.05). SMT decrease (P<0.05) from 0.70 to 0.68 sec only by changing PR from 60:40 up to 70:30. MMT decreased (P<0.05) by changing PR from 60:40 to 65:35 or to 70:30, being 4.2, 3.9 and 3.8 min, respectively. MFR increased (P<0.05) from 2.3 to 2.4 kg/min only by changing PR from 60:40 to 65:35. Percentage of SMY relative to TMY  decreased (P<0.05) from 2.7% at 60:40 to 2.4% to 2.4% at 65:35 and changing PR to 70:30 decreased (P<0.05) percentage of SMY to TMY to 2.3%. SMY, ST, TMT, SMT, MMT and SMY relative to TMY were higher (P<0.05) with claw size of 150 than 350 cm³. However, TMY and MMY were higher  (P<0.05) with claw size of 350 than 150 cm³. Increasing claw size from 150 to 350  increased (P<0.05) MFR from 2.2 to 23.5 kg/min, increased (P<0.05) MMY from 8.9 to 9.3 kg and decreased TMT, whereas SMY was the same in both cases of claw size. Using Duovac unit resulted in increase (P<0.05) in MMY from 9.0 to 9.2 kg and in TMY from 9.3 to 9.4 kg and decrease (P<0.05) in ST and MMT leading to reduction (P<0.05) in TMT from 4.9 to 4.5 min and increase (P<0.05) in MFR from 2.3 to 2.5 kg/min as compared to without using. Values of SMY decreased (P<0.05) from 0.3 to 0.2 kg and TMY increased (P<0.05) and SMY relative to TMY decreased (P<0.05) from 2.8 to 2.1%.