A dust collection sensing device of an automatic cleaner comprises: a main body with a placing chamber provided inside and a channel is provided on a side of the placing chamber, a dust collecting box installed within the placing chamber and an extended vacuuming pipe being provided on a side of the dust collecting box with an end thereof extending though the channel, a sensing assembly comprising a signal sending element and a signal receiving element, which are installed separately on the two opposite wall surfaces of the channel and are corresponding to the two sides of the bottom of the vacuuming pipe, and a warning indicator installed on the main body and connected to the signal receiving element of the sensing assembly electrically.