In order to meet the demands of reliability and time-determination in wireless industrial network, and considering the features of limited resources in Low-Rate WPAN(Wireless Personal Area Network), we present a reliable routing protocol for WIA-PA (Wireless Networks for Industrial Automation-Process Automation) wireless industrial networks in this paper. We first develop an improved routing mechanism with feedback and redundancy. Then a deterministic routing algorithm for both cluster and mesh networks is proposed based on it. The algorithm supports deterministic schedule, redundancy, and VCR (Virtual Communication Relationship) for aggregation. The experiment results show that the proposed routing protocol has the advantages of energy-saving, determination, high reliability and low complexity. The protocol is efficient and easy to implement in the practical wireless industrial networks.