In this paper, we propose a method based on improved perturbation and observation (I-P&O), which when used in conjunction with voltage and current sensors, enables the maximum power point tracking (MPPT) of the photovoltaic module array (PVMA), thereby increasing the power generation performance of the PVMA. The change in the maximum power output of the PVMA with varying sunlight intensities and temperature differences leads to a prolonged tracking time if the traditional perturbation and observation (P&O) method with small step-size tracking and a fixed value were adopted to find the maximum power point (MPP). Conversely, the adoption of a large step-size and a fixed value, even though the tracking speed is improved, causes a high amplitude oscillation around the point when tracked to the MPP, reducing the overall output power of the PVMA. Thus, an I-P&O method is proposed to solve this problem and to increase the output power of the PVMA. First, we set the initial voltage of the MPPT to 0.8-fold the voltage Vmp of the MPP for the PVMA under standard test conditions. At the same time, we auto-adjust the tracking step-size according to the slope value of the P–V characteristic curve for the PVMA. Then, we use 62050H-600S, a programmable DC power supply manufactured by Chroma ATE Inc., to simulate the output characteristics of a 5-series and 2-parallel PVMA, followed by tracking its MPP by the traditional P&O and I-P&O methods. Finally, from the experimental results, we proved that the proposed I-P&O method yields both a better tracking dynamic response and steady-state performance under different sunlight and temperature conditions.