Nanodosimetry simulates the biological effects of radiation by measuring physical quantities, such as ions that are ionized by initial particles. The microchannel ionized ion counting nanodosimeter can measure ionized ions by utilizing an internal electric field to drive them into the microchannel, where they induce an electron avalanche under high voltage. This paper studies the parameter design of a nanodosimeter utilizing microchannel ionized ion counting, based on finite element analysis and the Monte Carlo method. COMSOL finite element analysis and Garfield++ Monte Carlo software are utilized to calculate and simulate the static electric field, the dynamic transport of ionized ions, and the formation of electron avalanches in microchannels. The characteristics of the internal electric field funnel effect were systematically studied under various anode and cathode electric field configurations. Additionally, the impact of these configurations on the dynamic transport and collection efficiency of ionized ions was analyzed. The dependence of electron avalanche on design parameters, such as electric field configuration and microchannel diameter, is examined, and the results are discussed and summarized. The analysis results indicate that selecting an anode voltage of 5~15 V, a cathode voltage of -1 500~-2 000 V, and a microchannel diameter of 0.5~0.75 mm can achieve good measurement performance. The research findings presented in this article will provide a crucial theoretical foundation for a deeper understanding of the internal mechanisms and parameter design optimization of nanodosimeters.