Using SiO2 as the carrier and hexadecanol-palmitic acid-lauric acid as a phase change material, SiO2-based phase change and humidity controlling composite materials were prepared by the sol-gel process. The effects of solute concentration, ultrasonic time, ultrasonic power and dispersing medium on the particle size measurements were investigated by using median particle diameters (d50) as an evaluation indicator. The results indicated that the laser particle size analyzer (test range 1~10000 nm) is applicable to the particle size measurement of SiO2-based phase change and humidity controlling composite materials showing high reproducibility. The dispersion effect of water is better than that of alcohol. When the solute concentrationwas 5~10 g/L, the needed ultrasonic time was longer than 15 min and ultrasonic power was higher than 400 W, optimum dispersion results of SiO2-based phase change and humidity controlling composite materials can be achieved using water as the dispersing medium.