A novel pulse fitting analysis (PFA) method is presented for the acquisition of nuclear spectra. Thecharging process of the feedback capacitor in the resistive feedback charge-sensitive preamplifier isequivalent to the impulsive pulse, and its impulse response function (IRF) can be obtained by non-linearfitting of the falling edge of the nuclear pulse. The integral of the IRF excluding the baseline representsthe energy deposition of the particles in the detector. In addition, since the non-linear fitting process inPFA method is difficult to achieve in the conventional architecture of spectroscopy system, a new multichannel analyzer (MCA) based on Zynq SoC is proposed, which transmits all the data of nuclear pulsesfrom the programmable logic (PL) to the processing system (PS) by high-speed AXI-Stream in order toimplement PFA method with precision. The linearity of new MCA has been tested. The spectrum of 137Cswas obtained using LaBr3(Ce) scintillator detector, and was compared with commercial MCA by ORTEC. The results of tests indicate that the MCA based on PFA method has the same performance as thecommercial MCA based on pulse height analysis (PHA) method and excellent linearity for g-rays withdifferent energies, which infers that PFA method is an effective and promising method for the acquisitionof spectra. Furthermore, it provides a new solution for nuclear pulse processing algorithms involvingregression and iterative processes