To improve the accuracy of the visibility measurement and the evaluation of the measurement results, one method of changing baseline lengths visibility measurement is proposed. The least squares method is used to reduce the impact of errors of the position of the receiver and transmittance measurement on extinction coefficient. This can improve the measurement accuracy of the extinction coefficient. To verify the effectiveness of the method and evaluate the performance of the method under different visibility conditions, one mobile measuring platform is designed. Meanwhile a continuous atmospheric environment changing from high to low visibility is simulated in the atmospheric simulation chamber. In the simulation chamber, using the mobile platform, multi-point and multiple times measurements method is used to measure the extinction coefficient under different visibility conditions. The results show that this method has a high measurement stability and consistency under different visibility conditions. In the fitting process, coefficient of determination R2 increases with the visibility decreasing. When visibility is more than 3000 m, coefficient of determination can reach 0.9. Coefficient of determination can reach 0.99 in lower visibility. The unit weight variance is between 10^-4 and 10^-2 regardless of high or low visibility, this indicates the method has very smaller discrete and higher accuracy, which makes it potential to be used as the calibration of instrument and calibration of reference.