Abstract: There are two methods for measuring the sound reduction index (SRI) of large partitions. One is a conventional method which requires a sound proof chamber by reference to GB/T 19889.3-2005; the other is called sound intensity method by reference to ISO 15186-1:2000. The SRIs of three panels are measured according to these two methods. The results indicate that the SRI is almost consistent with the two methods in the middle and high frequency region. When the frequency is below 400 Hz, the SRI measured by sound intensity method is less than that measured by the conventional method. The effects of sound absorbing materials and the distance of spacers used in sound intensity probe are also investigated.