Abstract: Based on ECAH theoretical model, the measurement theory and test method of average nanoparticle size and particle size distribution of the titania nanoparticles in dispersive solution using ultrasonic wave with low and medium frequencies were studied. Through the establishing of relation between nanoparticle size distribution and ultrasonic attenuation spectrum, the nanoparticle size distribution could be obtained by optimal regular optimization algorithm inversion. The results show that the test results obtained by the method agreed well with the measurement results of TEM images and high speed centrifugal sedimentation nanoparticle analyzer, which indicated that measuring the particle size distribution of nanometer particles with the method was feasible and reliable.