Abstract: For phased array feeds, its front-end Low Noise Amplifier(LNA) noise figure directly affects the overall system performance, in technical way, one of the keys to reduce front-end LNA noise figure is impedance matching which means matching the active front-end with array elements. Impedance matching for a single antenna can be implemented by making antenna input impedance equal to amplifier optimal source impedance. However, the active impedance matching for PAF is complicated because active impedance depends on the beamforming coefficients. In this paper, we use HFSS-MAT-LAB co-simulation approach to design antenna and LNA for the phased array feeds with reflector, and optimize antenna parameters and optimum source impedance automatically to implement the active impedance matching and multibeam average noise optimization. Finally system simulation results verify the validity of this two methods.