The principle of maximum conformality (PMC) provides a way to eliminate the conventional renormalization scale ambiguity in a systematic way.By applying the PMC scale setting,all non-conformal terms in a perturbative series are summed into the running coupling,and one obtains a unique,scale-fixed prediction at any finite order.In this study,we make a detailed PMC analysis for the spin-singlet heavy quarkoniums decay (into light hadrons) at the next-to-leading order.After applying the PMC scale setting,the decay widths for all those cases are almost independent of the initial renormalization scales.The PMC scales for ηc and hc decays are below 1 GeV;to achieve a confidential pQCD estimation,we adopt several low-energy running coupling models to carry out the estimation.By taking the MPT model,we obtain Г(ηc → LH) =25.09+552-4.28 MeV,Г(ηb →LH) =14.34+0.92-0.84 MeV,Г(hc → LH)=0.54+0.06-0.04 MeV and Г(hb → LH) =39 89+0.28-0.46 keV,where the errors are calculated by taking mc ∈[1.40GeV,1.60GeV] and mb ∈[4.50GeV,4.70GeV].These decay widths agree with the principle of minimum sensitivity estimations,in which the decay widths ofηc,b are also consistent with the measured ones.