The invention provides a grass trimmer and a cord delivering method for a grass trimmer, the grass trimmer includes an extending rod, an housing, a grass trimming head, a handle, a main motor and a main switch, wherein the grass trimming head includes a base, a cap and a spool having a first state relative static with the base, and the grass trimmer further includes a cord delivering mechanism; the cord delivering mechanism includes a cord delivering electronic switch independent of the main switch and a control device; and the cord delivering electronic switch operably electrically controls the control device to enable the spool to be in a second state capable of generating a rotary speed difference with the base. An operator does not need to interrupt work of the grass trimmer and can timely pay off required and the cord delivering operation is simple and convenient.