The invention relates to a cleaning method for redundant sand in the inner chamber of an integrated core for 3D printing. The core is an integrated 3D printing core, a plurality of cavities are formed in the core, unbonded loose sand is stacked in the cavities, and a plurality of sand discharge holes communicated with the internal cavities are formed in each surface of the core. During cleaning of the loose sand in the inner chamber of the core, firstly, preliminary vibrating sand removal is performed in the way that the loose sand in the inner chamber is discharged out of the sand discharge holes in a vibrating manner to perform preliminary sand removal, and after that, fluid scouring sand removal is performed in the way that a fluid is injected into the inner chamber of the core at a certain flow rate and the flow-in and flow-out directions are continually changed to change the flowing direction of the fluid in the cavities so as to enable the fluid to flow through and scour the cavities of the core, low-hardness transitional sand layers on the inner walls of the cavities are impacted under the scouring and stripping actions of the fluid, and the scoured sand is discharged along with the fluid. According to the cleaning method, as the plurality of sand discharge holes connected with the inner chamber are additionally formed, sand removal of the cavities of the integrated 3D printing core can be realized through vibratory sand discharging and fluid scouring sand discharging.