Input-series-output-parallel (ISOP) inverter system is very suitable for high input voltage and high output current power conversion applications. If the inverter system topology is applied to the grid-connected application, a large-capacity grid-connected inverter system can be built with multiple small-capacity standardized inverter modules, which will improve system reliability and facilitate system design. This paper investigates on ISOP LCL-type grid-connected inverter system, and it proposes a topological optimization method to cut the number of inductor and reduce system volume. Then a new solution is presented, which can meet multiple control targets, i.e., power balance among modules, damping resonant peak, and high power factor of the grid current. Simulation and experimental results validate the effectiveness of the proposed topology and solution.