Background: We estimated the predictive effects of ART-related perceptions on the actual ART uptake behavior among ART naïve PLWH stratified by different time of HIV diagnosis under the new strategy. Methods: A prospective cohort study was conducted among ART naïve PLWH in Guangzhou, China from June 2016 to June 2017. Cox regression model was used to evaluate the predictive effects of ART-related perceptions on ART initiation among PLWH stratified by different timepoint of HIV diagnosis (i.e., before or after the update of the new treatment policy). Results: Among 411 participants, 150 and 261 were diagnosed before (pre-scaleup group) and after (post-scaleup group) the implementation of the new strategy, respectively. The ART initiation rate in the post-scaleup group (88.9%) was higher than that in the pre-scaleup group (73.3%) (p<0.001). A significant difference of mean score was detected in each HBM construct between pre- and post- scaleup groups (p<0.05). After adjusting for significant background variables, among all participants, only the self-efficacy (adjusted HR (HRa) =1.23, 95% C.I.: 1.06 to 1.43, p=0.006), has a predictive effect on ART initiation; in pre-scaleup group, all constructs of HBM-related ART perceptions were predictors of ART initiation (HRa=0.71 to 1.83, p<0.05), while in post-scaleup group, no significant difference was found in each construct (p>0.05). Conclusions: The ART initiation rate was high particularly among participants who diagnosed after the new treatment strategy. The important role of the time of HIV diagnosis on ART initiation identified in this study suggested that future implementation interventions may consider to modify the ART-related perceptions for HIV patients who diagnosed before the implementation of the new ART strategy, while expand the accessibility of ART service for those who diagnosed after the implementation of the new strategy.