Abstract: The key to the formation of maximum fuel-air cloud detonation after the dispersion of fuel-air explosive (FAE) is whether the secondary detonation fuze can detect the optimal cloud detonation concentration quickly and accurately in a very short rendezvous time.The feasibility of the method of rapidly detecting the cloud concentration by using the echo attenuation of pulsed ultrasound in cloud is verified by test and simulation tools. For the accuracy and rigor of the test results，the cloud concentration in the fuze channel detected by the fuze prototype in the high dynamic rendezvous environment can not be regarded as the same as the preset environmental concentration. The computer numerical simulation method is used to simulate the gas-solid two-phase fluid concentration distribution in the fuze and cloud rendezvous process under 100 m/s test conditions. The experimental results show that the simulated concentration of fuze channel is consistent with the attenuation rate of pulsed ultrasonic propagation in the channel in the rendezvous environment with concentration of 75 g/m³，150 g/m³ and 225 g/m³，which provides an analysis means to improve the optimal initiation of FAE weapons.

Key words: fuel-airexplosive, fuze, cloud, concentrationdetection, numericalsimulation, ultrasonicattenuation