With the application of two-stage PV grid-tie inverter in the large-scale and medium power systems, it is widely researched that the LVRT control strategy of photovoltaic inverter based on the two power stages topology. Compared with single-stage PV inverter, it is a combination of the first power stage of DC/DC converter and the second power stage of DC/AC inverter for two-stage PV inverter. The control is more complex and it is more difficult in the low voltage ride through. Firstly, the system modeling is carried on and then the control strategy is proposed based on control mode seamless switching in LVRT. At the steady state the DC/DC conversion unit tracks the maximum power point and the DC/AC inverter unit works as a constant voltage source. In LVRT, the DC/DC conversion unit runs in the constant busbar voltage mode and DC/AC inverter unit runs in the p-q mode. The problem is resolved that the DC bus over-voltage caused by unbalanced energy between the DC/DC unit and DC/AC unit. The experiments in a 40 kW PV grid-tie inverter of two power stage verify the correctness and feasibility of the theoretical analysis finally.