A speed-measuring device with large area light screen is introduced.The horizontal distance of light screen is 6 000 mm

which avoids the shortcomings of small testing area of bullet speed testing device

short safe distance and easy-breaking.This device is composed of laser optical system

regression-reflective material（retro-reflective sheeting）

fixing frame

reflective mirror

photoelectric detector and processing circuit.The laser is projected to the retro-reflective sheeting on the other side to form a light screen detecting area.The light flux is changed when bullet or debris with high speed pass through the light screens

and the passing target speed can be achieved by time-measuring device or data acquisition system.A comparing experiment has been done by using 7.62 mm projectile and mature frame style 800 mm×800 mm light screen

and the result can meet the precision requirement.The experimental results indicate that the device has distinguish advantages such as large target surface area

high precision

convenient for using and maintenance

low-cost and so on.The device can be also used for velocity measurement of large caliber projectile and projectile fragments.