In order to solve the problems of traditional atmospheric transmissometer, such as fixed transmitting-receiving baseline, limited sampling space, and poor applicability of transmittance model, a variable baseline atmospheric visibility measurement system is designed in this work. The laser emission unit of the system is fixed, while the optical receiving unit is movable, so the atmospheric transmittance can be obtained at different baseline lengths. By measuring the multi-point atmospheric transmittance and using the least square fitting, the atmospheric extinction coefficient and the atmospheric visibility can be obtained. Simulation experiments of the proposed system and the traditional transmissometer are carried out under the atmospheric visibility conditions of 200, 800, and 2000 m. The results show that the root mean square error of atmospheric extinction coefficient measured by the proposed system is less than that of the traditional transmissometer, which effectively reduces the influence of system error and random error on the measurement results. The effectiveness and reliability of the system are verified by the external field experiment in the atmosphere environment simulation chamber.