Raindrop identification is important in automated weather observations, weather radar calibration and other related research areas. As to measurement of raindrop shape, two-dimensional video disdrometer’s principle, main technical parameter, function and application are concluded firstly, then a precipitation slit photography based on linear CCD is put forwarded, the process of linear scanning and the reconstruction process of precipitation are analyzed, the measuring optical system with telecentric optical system as imaging system and Cora illumination as lighting system are designed, which can realize uniform lighting and high precision measurement, and prospective problems were analyzed at last.