On the basis of the theoretical derivation of three-dimension sound intensity arrays in plane wave,firstly,the sound pressure and the particle velocity are estimated,and the sound intensity spectrum is calculated.Then,a comparison of amplitude bias and directional bias is made between a tetrahedral microphones system and a six-mi- crophone system.Finally,the numerical simulation results are verified through experiments in an anechoic cham- ber.It is found that (1) the magnitude bias expands exponentially as frequency increases; (2) the amplitude bia- ses of the two systems are both less than 0.5dB within the range from 0Hz to 4kHz,which means that the systems both meet the accuracy requirements; (3) the tetrahedral microphones system is superior to the six-microphone sys- tem; and (4) the directional bias of six-microphone system is close to 6° at a frequency of 8kHz,while that of tetra- hedral approach is only 1° and increases slowly in the whole frequency domain,which means that the tetrahedral microphones system exhibits higher directional accuracy than the six-microphone system.