  We explore the breaking effects of the $SU(3)$ flavor symmetry in the singly
Cabibbo-suppressed anti-triplet charmed baryon decays of ${\bf B}_c\to {\bf
B}_n M$, with ${\bf B}_c=(\Xi_c^0,\Xi_c^+,\Lambda_c^+)$ and ${\bf B}_n(M)$ the
baryon (pseudo-scalar) octets. We find that these breaking effects can be used
to account for the experimental data on the decay branching ratios of ${\cal
B}(\Lambda_c^+\to \Sigma^{0} K^{+},\Lambda^{0} K^{+})$ and $R'_{K/\pi}$=${\cal
B}(\Xi^0_c \to \Xi^- K^+)$/${\cal B}(\Xi^0_c \to \Xi^- \pi^+)$. In addition, we
obtain that ${\cal B}(\Xi_{c}^{0} \to \Xi^{-} K^{+},\Sigma^{-} \pi^{+})=(4.6
\pm 1.7,12.8 \pm 3.1)\times 10^{-4}$, ${\cal B}(\Xi_c^0\to
pK^-,\Sigma^+\pi^-)=(3.0 \pm 1.0, 5.2 \pm 1.6)\times 10^{-4}$ and ${\cal
B}(\Xi_c^+\to \Sigma^{0(+)} \pi^{+(0)})=(10.3 \pm 1.7)\times 10^{-4}$, which
all receive significant contributions from the breaking effects, and can be
tested by the BESIII and LHCb experiments.
