A drain valve base includes an upper connection seat and a lower connection seat which are integrally formed. The upper connection seat is connected with the lower connection seat by connection arms which are provided at intervals, and hollow portions are provided between every two connection arms. A through drain outlet is formed in the center portion of the lower connection seat, and an annular surface is formed on the top of the lower connection seat. A water-seal convex ring is formed on a side part of the annular surface which is adjacent to the inwall of the drain outlet. A water-seal surface is formed on the top of the water-seal convex ring, and blocking devices which can stop water flow are provided on the inner side and the outer side of the water-seal convex ring.