As a prototype of Deep Underground Neutrino Experiment far detector, ProtoDUNE single-phase liquid argon Time Projection Chamber will sit in H4 beam line at CERN to study detector response to particles. It consists of 6 full-size Anode Plane Assemblies (APAs) plus 2 Cathode Plane Assemblies (CPAs) to form two 3.6m drift regions with total 15,360 readout channels. To achieve optimal noise performance, readout electronics developed for extremely low temperatures (77K-89K) operation has been studied with an integral design concept of APA, cold electronics, feed-through, plus warm interface electronics with local diagnostic following strict isolation and grounding rules. By the end of September 2017, the first full-size APA has been integrated with readout electronics successfully for the coming cold integration test at CERN.