The friction coefifcients between the surfaces of a ball and a disc lubricated by a space lubricating oil No.4129 were measured at various operating conditions on a ball-disc friction test rig. Friction characteristic curves were obtained under sliding and rolling movements at point contact. A new model for calculation of the friction coefifcient was pre-sented. The results show that the bigger the load is, the larger the friction coefifcient becomes. The rolling speed ranging from 1 m/s to10 m/s has an important effect on the friction coefifcient. The friction coefifcient increases with the increase in sliding speed and the decrease in rolling speed. The linear variation region of the friction coefifcient versus the sliding speed at high rolling speed is wider than that at low rolling speed. The model for calculation of the friction coefifcient is accurate for engineering use.