The invention belongs to the technical field of fluid dynamics test devices, and discloses a flow pattern generator. The flow pattern generator comprises a liquid inlet, a gradually widening apertureconnected with the liquid inlet, a first flange connected with the gradually widening aperture, a flow pattern generation area connected with the first flange, a second flange connected with a flow pattern generation area, a flow pattern observation measuring tube one end of which is connected with the second flange, and an end cover connected with the other end of the flow pattern observation measuring tube; the flow pattern generation area is provided with a liquid injection port and a gas injection port, and the end cover is provided with a liquid outflow port and a gas outflow port. According to the technical scheme, the flow pattern generator is simple, small, low in cost, high in operability and capable of meeting various experimental requirements for bubble flow, slug flow, blocky flow, annular flow with fibers, annular flow and the like.