Matrix rectifier (MR) is a buck rectifier in nature, which can be reduced from the traditional matrix converter. Like other converters interfaced with the power lines, it hardly avoids the problems caused by the abnormal cases of three-phase input voltages. The existing basic PWM algorithms of MR include current SVM algorithm and switching function algorithm, suitable for normal power supply. In view of this, after deriving the input current SVM algorithm under balanced condition, a modified input current SVM algorithm is derived under imbalanced conditions based on the concept of switching function algorithm. The practical simulation model of MR is then built up and its working principle is realized by employing simulation software SIMULINK6.0. The simulation analysis results of MR are also offered, including input voltage waveforms, input current waveforms and output DC voltage waveforms, which are consistent with the theoretical analysis results