A flexible substrate, a display device and a method for bonding an electronic device onto a flexible substrate are disclosed. The flexible substrate includes a base substrate, the base substrate includes a bonding portion for bonding an electronic device and an auxiliary bonding portion integrally formed with the bonding portion, the auxiliary bonding portion and the bonding portion are disposed back to back, and the bonding portion completely falls into a region where the auxiliary bonding portion is provided in an orthographic projection direction. With an auxiliary bonding portion being disposed beside the bonding portion for bonding the electronic devices such as ICs and FPCs, when bonding the electronic device onto the bonding portion, the auxiliary bonding portion can enhance the strength of the bonding portion and improve the bonding alignment precision and contact property of the electronic device, which further improves the non-defect ratio of the flexible display device and has a lower cost.