Electronic transaction method and system and payment platform system

The invention provides an electronic transaction method and system and a payment platform system. The electronic transaction method adopts a merchant transaction system, a banking system, a payment gateway and the payment platform system, wherein the payment platform system is communicated with the merchant transaction system through the payment gateway and communicated with the banking system through the payment gateway. The electronic transaction method comprises the steps: the payment platform system receives an agreement deduction request sent by the merchant transaction system; the payment platform system verifies the agreement deduction request; the payment platform system is communicated with the banking system to perform money deduction according to the agreement deduction request and a preset payment deduction agreement after the agreement deduction request is validated. A user does not need to log in the payment platform system by means of the electronic transaction method, processes are simplified, and the electronic transaction method is quick, convenient, safe and efficient.