The invention provides a photovoltaic power generation grid-connected system. The photovoltaic power generation grid-connected system comprises a grid-connected device and a photovoltaic array, wherein the grid-connected device is connected in series with the photovoltaic array; the grid-connected device and the photovoltaic array are connected between two ends of a direct-current bus; an output voltage of the grid-connected device is adjustable; the two ends of the direct-current bus comprise a positive electrode and a negative electrode of the direct-current bus, the positive electrode of the direct-current bus and the ground, or the negative electrode of the direct-current bus and the ground; and the grid-connected device is relatively low in capacity. Through adoption of the photovoltaic power generation grid-connected system, the problems of relatively large capacity, large size and relatively high manufacturing cost of a DC/DC (Direct Current to Direct Current) converter due to execution of maximum power tracking through the DC/DC converter in the prior art are solved; high performance of MPPT (Maximum Power Point Tracking) is ensured; and the service efficiency of a photovoltaic cell panel is increased.