In this work, load distribution on ball-screw systems (BSS) is determined by experimental techniques. Two optical techniques are used: photoelasticity for stress-field measurement and the mark-tracking method for displacement-field determination. In parallel to the experimental study, finite element method (FEM) and analytical solutions are used to calculate the loads applied on each ball of the BSS. Experimental results are used to validate the choice of boundary conditions and contact conditions between ball-screw and ball-nut in the FEM solution. The validation criterion is the correspondence between numerical and experimental fringes representing the differences of principal stresses. In addition to the study of load distribution, this paper presents the influence of the angle of contact direction on the stress distribution in BSS.