An online HPLC dissolution test system includes a dissolution tester and a liquid chromatograph. An autosampler of the liquid chromatograph includes at least one flow vial, a sampling needle and an injection port. the flow vial is connected to the dissolution tester via a pipe and is for storing a sample solution supplied from the dissolution tester therein. The sampling needle is for collecting the sample solution by sucking from the flow vial. The injection port is for injecting the sample solution from the sampling needle into the analysis channel. The controller of the liquid chromatograph includes an immediate analyzing execution part configured to cause the autosampler to execute immediate analyzing operation for sucking the sample solution in the flow vial with the sampling needle and directly injecting the sample solution into the injection port when the sample solution is supplied from the dissolution tester to the flow vial.