In order to develop the emergency plans of train leaving the storehouse in special weather conditions(fog, haze and soon), and accurately grasp the train emergency braking distance in different initial velocity, the test of Xi’an metro line 1 and 2 vehicleswas put forward in the test line. With the theoretical analysis and field validation test results, it was concluded: with the same brakingsystem, initial braking speed was larger, empty walk time influence on braking deceleration was smaller, and the average decelerationwas approaching instantaneous deceleration; in the same braking grade, although pure air brake and mixed electric brake both met thereduction speed requirements, but the deceleration values were different; in the different braking system, the designed and determineddeceleration limit value, the brake shoe material, empty walking time, the theoretical calculation model and the external test conditionswould influence the braking deceleration and braking distance.