We measured the single-molecule conductance of alkanedicarboxylic acid (HOOC-(CH2)(n)-COOH, n=1-5) with Pd nanoclusters by electrochemical jump-to-contact STM-break junction. They gave out decay constant beta(N) of 0.652 per (-CH2) unit and contact conductance of 97 nS. The single-molecule conductance of carboxylic acid binding to bulk metal electrode was also studied, and has almost the same value as that binding to Pd nanoclusters. The conductance study on Pd-oxalic acid junctions shows that the electron transfer through the ultrashort molecular junctions is not only contributed by the "through-bond" (TB) mechanism but also "through-space" (TS) mechanism. Our work provides a new path to study the single-molecule conductance with Pd contacts. (C) 2014 Elsevier Ltd. All rights reserved.