With the worldwide deterioration of environmental pollution and energy crisis, the exploration and development of new energy sources that are clean and renewable have gradually aroused much more attention from humans, which makes the application of the solar PV (photovoltaic) technology become more widespread. In this paper, a deep research on boost type PV generation system connected to a DC micro-grid has been done mainly from several aspects, such as the engineering model of PV cells, the MPPT (maximum power point tracking) technology and the performance simulation and digital realization of the system. According to the unimodality of P-U curve, a MPPT implementation plan based on the combination of impedance transformation of boost converter and incremental conductance technique has been determined, and the principle of achieving MPPT by incremental conductance technique has been analyzed in details. Considering the inherent defect of the fixed-step incremental conductance technique found in the simulation, a modified variable step incremental conductance MPPT control strategy has been introduced so as to solve the contradiction between tracking speed and steady-state accuracy, which exists in the traditional fixed-step incremental conductance technique. And, the variable step incremental conductance technique has been verified by simulation. and experiments have been conducted. The corresponding experimental results validate the efficacy and feasibility of the efficient PV generation system designed in this paper, which is with a function of MPPT.