The invention relates to an automatic flow discarding rainwater collecting down pipe which comprises a cavity, a rainwater container bottom plate, a rainwater collecting water inlet pipe, an initial rainwater control filter screen, a rainwater collecting delivery oblique plate, an initial rainwater automatic flow discarding funnel and a lower extending partition plate. The automatic flow discarding rainwater collecting down pipe has the advantages that the automatic flow discarding rainwater collecting down pipe is extremely simple in structure, quite easy and convenient to process and low in manufacturing cost and is small; the automatic flow discarding rainwater collecting down pipe can be used as rainwater storage equipment and is free of land occupation and influence on aesthetics; initial rainwater can be quickly and effectively drained, middle-stage and late-stage rainwater can be effectively collected, the rainwater can automatically overflow to be drained after the automatic flow discarding rainwater collecting down pipe is filled with the collected rainwater, accordingly, rainwater resources can be sufficiently utilized, and the water use safety can be guaranteed.