In this paper, we use transaction data in bag databases as the source data of mining, and each transaction data contains a consumer ever purchased items and the quantity of those items. We mine quantitative association rules from two aspects. One is to modify the FP-tree algorithm to mine quantitative association rules. The experiments show that the performances of our algorithm are faster than the MQA-1 algorithm [1, 9]. The other is to let one transaction item as the target of mining, and to present a more efficient algorithm to mine quantitative association rules which contain the item than the preceding algorithm.