In the paper, we study the properties of the top-quark $overline{rm MS}$ running mass computed from its on-shell mass by using both the four-loop $overline{rm MS}$-on-shell relation and the principle of maximum conformality (PMC) scale-setting approach. The PMC adopts the renormalization group equation to set the correct magnitude of the strong running coupling of the perturbative series, its prediction avoids the conventional renormalization scale ambiguity, and thus a more precise pQCD prediction can be achieved. After applying the PMC to the four-loop $overline{rm MS}$-on-shell relation and taking the top-quark on-shell mass $M_t=172.9pm0.4$ GeV as an input, we obtain the renormalization scale-invariant $overline{rm MS}$ running mass at the scale $m_t$, e.g., $m_t(m_t)simeq 162.6pm 0.4$ GeV, in which the error is the squared average of those from $Delta alpha_s(M_Z)$, $Delta M_t$, and the approximate error from the uncalculated five-loop terms predicted by using the Pad{e} approximation approach.
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