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<b>Background</b>: Starting from May 31 <sup>st</sup>, 2023,
the local transmission of monkeypox (Mpox) in mainland China began in
Beijing. Till now, the transmission characteristics have not been
explored. <b>Method</b>: Based on the daily Mpox incidence data in the
first three weeks of Beijing (from May 31 <sup>st</sup> to June
21 <sup>st</sup>, 2023) , we employed the instant-individual
heterogeneity transmission model to simultaneously calculate the
effective reproduction number ( <i>R</i> <sub>e</sub>) and the
degree of heterogeneity ( <i>k</i>) of the Beijing epidemic. We
additionally simulated the monthly infection size in Beijing from July
to September and compared with the reported data to project subsequent
transmission dynamics. <b>Results</b>: We estimated <i>R</i>
<sub>e</sub> to be 1.68 [95% HPD:1.12, 2.41], and <i>k</i> to
be 2.57 [95% HPD: 0.54, 83.88], suggesting the transmission of Mpox
in Beijing was supercritical and didn’t have considerable transmission
heterogeneity. We projected that <i>R</i> <sub>e</sub> fell in the
range of 0.95 to 1.0 from July to September, highlighting more efforts
needed to further reduce the Mpox transmissibility. <b>Conclusion</b>:
Our findings revealed supercritical and homogeneous transmission of the
Mpox epidemic in Beijing. Our results may provide reference for
understanding and predicting of the on-going Mpox transmission in other
regions of China and assess the effect of control measures.</div>