For measuring insertion loss, reflection and radiation of smoke screen, a 3mm wave electromagnetic characteristic measurement radar has been fabricated, which comprises a 3mm wave radar cross section (RCS) measurement radar and a 3mm wave radiometer. The transmitter and receiver of the former are separated, and each antenna of them can be chosen among three kinds of antennas with different beam width or gain, according to the sizes of object and the power of reflection signal. In order to fit the tremendous changes of power between transmission and reflection, the sensitivity and the dynamic range of the system is improved by millimeter wave fixed attenuator, switching between long range and short range, and digital intermediate frequency (IF) receiver with signal accumulating by Fast Fourier Transform Algorithm (FFT). In the 3mm wave super-heterodyne IF Dicke-radiometer, hardware integral and soft integral are both used to achieve high sensitivity. All the millimeter wave oscillators in the system are phase-locked. The interval between two adjacent data is 2ms, which is suitable for suspending and movable smoke screen.