An ice storage amount adjusting system is disclosed. The ice storage amount adjusting system includes a chiller, an air-condition scheduler for outputting a scheduling parameter of an air-conditioner during a first time, an indoor-temperature setting module for outputting indoor-temperature setting condition during the first time, a building exterior-load collecting module for outputting exterior loading factors of a building during the first time, a weather forecasting data collecting module for outputting weather forecasting data during an upcoming second time, and an air-condition loading predictor. The air-condition loading predictor predicts an air-condition loading of the air-conditioner at the second time based on the scheduling parameter, the indoor-temperature setting condition, the exterior loading factors and the weather forecasting data. The chiller adjusts its ice storage amount to reach a target storage demand based on the predicted air-condition loading.