Disclosed are a method and a system of calculating a sales commission using a transformation coefficient in on-line by reflecting sales of members receiving sales commissions and new sales of sub-members, and a record medium thereof. Members receive sales commissions based on members' own sales, so that old sub-members as well as new members actively sell commodities. The property of the tree to which the members belong is more increased, so that the members have reliability and affection for a company. The revenue of the members is more increased, and a company attempts to increase sales and members. A company determines sales commissions paid to members at a constant commission payment rate for the sales of the members without being affected by the enlargement of an organization due to the increase of the members and the amount of sales.