A method for measuring particle size distribution，density and concentration of nanometer suspension was proposed，and the measurement apparatus and system was designed.Meanwhile,the pulse echo mode was adopted to measure the attenuation spectrum of nano-antimony tin oxide（ATO）suspension at high frequencies.A wide-band ultrasonic transducer with a center frequency of 25 MHz（V324-SU，OLYMPUS） served as an emitter and a receiver simultaneously in the experiments.Then it can yield an ultrasonic spectrum over the frequency from 17 MHz to 26 MHz.The optimum regularization algorithm was applied to minimize the influence of ill-conditioned equation during the inversion of particle size distribution.The recovered median size D50 of nano-ATO was 22.07 nm which was in agreement with that of the sedimentation method with the error no more than 0.1%.At the same time，the multiple reflection approach was employed to obtain the ultrasonic impedance of the nanometer suspension.Several groups of superb ultrasonic signals consisting of more than 12 pluse-echoes in each one，were acquired with the same ultrasonic transducer.The ultrasonic velocity，overall density and concentration of the aqueous ATO suspensions can be determined based on the mathematical derivation and acoustic theory.Experimental results showed that the error of density and concentration was within 0.6% and 8%,respectively.Due to its avantages of reliable principle,simple apparatus and time-saving，the proposed method could provide an online monitoring for the particle size,density and concentration of nano-particle materials during the processing and preparation.