In petroleum industry, fiber containing fluids are widely used to improve solid transport capacity of drilling/fracturing fluids. The settling velocity of particle in fiber containing fluids is studied to provide basis for the evaluation and optimization of the fiber drilling/fracturing fluid performance. The purpose of current study is to develop the prediction model, suitable for different particle Reynolds numbers and fiber concentrations, for settling velocity of solid spheres in fiber containing power-law fluids. Settling tests were conducted in fiber containing power-law fluids, and 4 crucial factors were considered, involving fluid rheology, sphere diameter, particle density and fiber concentration. Results show that adding a small amount of fiber makes a minor increase in the apparent viscosity of the base fluids under the experimental condition, and sphere settling velocity drops slowly with fiber concentration increasing. It indicates that an additional drag force, defined as fiber frag force, is applied to the sphere by fiber network. Similar to the definition of the viscous drag coefficient, the fiber drag coefficient is defined to quantify the fiber drag force. the dimensionless number known as Archimedes number is defined by combining total drag coefficient (sum of the fiber drag coefficient and viscous drag coefficient) and Reynolds number. The Archimedes number and Reynolds number follows linear relationship in the log-log plot. Finally, the prediction model for settling velocity of solid spheres is obtained by the regression equation of the Archimedes number and particle Reynolds number. The model predicts settling velocity in good agreement with measured settling velocity, with average relative difference of 12.39%. The model is valid for a range of particle Reynolds number (0.002–324) and fiber concentration (0.02%–0.1%). This study is with the guiding significance for the better application of fiber in petroleum engineering.