Abstract: Vacuum system is an important part of the fusion device, and vacuum system of EAST mainly includes cryogenic superconducting vacuum vessel and plasma discharge vacuum vessel. The plasma discharge vacuum vessel is also known as the inner vacuum vessel and the inner vacuum pumping system directly affects the removal of particles from the device and the achievements of high-parameter plasma discharges. The improved inner vacuum pumping system of EAST mainly includes main pumping subsystem, divertor pumping subsystem and lower hybrid wave heating system pumping subsystem. There are 6 molecular pumps, 14 outer cryopumps and 2 inner cryopumps used for the whole pumping system. The gas balance method was used to calibrate the pumping speed of each subsystem. The experimental results showed that the pumping speed is the highest at the pressure ranging from 5×10⁻⁴ to 5×10⁻³ Pa in the inner vacuum vessel, and the pumping speed of each subsystem decreases with the increase or decrease of the vacuum vessel pressure. Compared with the total pumping speed before and after the improvement, the maximum pumping speed after the improvement can reach 170 m³/s, and the overall pumping speed can be increased by about 20%. Under the hundred-second plasma discharge parameters, the retention of fueling particles is preliminarily evaluated by calibrated pumping speed. This study provides data support for wall retention and recycling control of plasma discharge and other related physical experiments.