Parameter models of two typical coordinate measuring systems of a line-structured light visual sensor and a symmetrical binocular visual sensor are investigated with the trigonometric method. By analyzing the relations between the coordinate measuring models and the structural parameters of the two typical visual sensor systems,the effect of the visual sensor structural parameters and their calibration errors on the sensor measurement result is investigated. The error analysis explicitly illustrates the dependence of the visual sensor accuracy on the sensor structural parameters. Lastly,based on the comprehensive consideration for designing an ideal visual sensor,the optimum rules of structural parameters are proposed,and the design methods of the two typical sensors are derived.