When the capacity of photovoltaic system is relatively large in DC microgrid, the photovoltaic (PV) system should have the function of bus voltage support. Firstly, a supportive relationship between the output power of PV and the bus voltage of DC microgrid is constituted in this paper, and the real-time photovoltaic output P-V curve is fitted based on sampling values by using the Newton difference method, then the DC voltage control reference value is calculated according to the real-time fitted P-V curve and the relationship between the output power of PV and the bus voltage of DC microgrid. The economy and voltage support capability of photovoltaic generation are considered comprehensively by introducing the output coefficient, and adaptive voltage support is achived by selecting output coefficient through adaptive strategy. Moreover, the maximum power point tracking and constant power control are integrated in this strategy.The principle of this strategy is simple and easy to be realized, it improves the utilization efficiency of PV power generation without narrowing voltage support range for DC bus voltage, and also can enhance the ability for photovoltaic power generation in multiple scenes. Simulation results verify the effectiveness and superiority.