Minimization of the channel-to-channel variation of silicon photomultiplier (SiPM) array is of great importance in achieving high performance for SiPM based imaging detectors. The purpose of this study was to characterize the operating parameters of a large-area SiPM based detector module with 12x12 pixel array (SensL's ArraySM-4P9) in order to develop an optimal multiplexing readout for high-resolution SPECT imaging. Two versions of SensL's SiPM arrays were investigated in this study. The previous ArraySL-4 version has an array of 4x4 pixels with 3x3mm2 pixel size and the new AarraySM-4p9 version consists of a 3x3 matrix of the 4x4 pixels SiPM modules. The current versus voltage (I-V) characteristics of individual SiPM pixels were measured to extract information of its breakdown voltage and dark current. The energy spectrum of individual pixels coupling with a 1x1x3mm3 LYSO crystal was measured using 22Na and 137Cs sources. The test results show that the previous ArraySL-4 version has larger channel-to-channel variations in breakdown voltage and dark current than the newer AarraySM-4p9 version. The new large-area ArraySM-4P9 SiPM module with 12x12 pixels shows very small breakdown voltage variations within ±0.1V at operating voltage of ∼27V and dark current variations within ±0.4nA of ∼1nA over the entire 144 pixel elements. The measured energy resolution of an individual SiPM pixel with a 1x1x3mm3 LYSO crystal is ∼16% at energy of 662keV. In conclusion, the new SensL's AarraySM-4p9 ArraySM has much better improved property than the previous ArraySL-4 version. The excellent performance uniformity of the large-area ArraySM-4P9 SiPM module is good for multiplexed readout approach in the development of high-performance and cost-effective compact imaging detectors. 2013 IEEE.