Blade lengthened type fan

The invention relates to a blade lengthened type fan which comprises a tower drum, a hub, blades, a transmission device and a power generating device. Each blade comprises a blade main body portion and a blade lengthened portion. Each blade lengthened portion is connected with one end of the corresponding blade main body portion, and an opening is formed in the end, connected with each blade lengthened portion, of the corresponding blade main body portion; a supporting structure in the blade main body portion and/or the blade lengthened portion of one blade is connected with a supporting structure in the blade lengthened portion or the blade main body portion of another corresponding blade through the corresponding opening.