In order to decrease the minimum detection limit (MDL) and increase the dete ction sensitivity,a novel asymmetric ellipsoid light-collector multi-pass gas-cell is proposed fo r the application in mid-infrared CH_{4concentration} detection.Under the full consideration of foot -prints and sizes of wire light-source and dual-channel detector,thorough modeling on the light co llector gas-cell is established,and formulations and expressions including direct incident power,r eflected incident power,light collection efficiency and sensitivity-related coefficient are deri ved.Through calculation and analysis,parameter conditions are obtained for achieving both h igh light collection efficiency and high sensitivity-related coefficient,the structural parameters of the gas-cell are derived,and the gas-cell is then fabricated.Based on the fabricated gas-ce ll with optimized parameters, the CH_4detection system is established,and detection performance is demonstra ted.Experimental results show that the minimum detection limit is about 5×10－6,the detection sensitivity is determined to be about 6－7×10－6 under the low concentration range of 0－100×10－6, within high concentration range of 1－40×10－3,the detection sensitivity decreases as the concentration increases,which varies from 20×10－6 to 160×10－6.Due to car eful design and optimization on asymmetric ellipsoid gas-cell,this detection system exhibits good performance including higher detection sensitivity and lower MDL.