The invention relates to an inlet flow guide device for improving cavitation performance of a shield pump, and belongs to the field of fluid machinery. Under the premise that other main components inthe pump are not changed, only an impeller nut (4) is replaced, a fixed guide blade (2) and a flow guide pipe (3) are additionally mounted, inner circulating cooling liquid is guided to the position far away from an impeller suction inlet (51), direct impact of high-speed outflow on a low pressure area of the impeller suction inlet (51) is changed, therefore the inflow condition is improved effectively, the cavitation performance of the shield pump is improved, and the inlet flow guide device is simple, convenient, efficient, low in cost and high in universality.