In this work, we study the constraints on the scenario of light stops and sbottoms in the next-to-minimal supersymmetric standard model (NMSSM), especially by a 125 GeV Higgs boson discovery and the LHC bounds on supersymmetry. The constraints from dark matter detections are also taken into account. From the parameter scan, we find that the NMSSM can well accommodate a light Higgs boson around 125 GeV and decay patterns. We would like to stress that the LHC direct supersymmetry searches with b-tagging are very powerful and can set strong bounds on many NMSSM parameter points with light stops and sbottoms. We find $\tilde {t}\to b\tilde��^+_1$ is a very promising channel for light stop detection if the mass splitting between $\tilde��^+_1$ and $\tilde��^0_1$ is very small. It is also pointed out that in order to close the parameter space of light stops and sbottoms, new search strategies for signal channels such as $p p \to {\tilde t_1} {\tilde t_1} \to t {\bar t} h h \tilde��^0_1 \tilde��^0_1$ and $p p \to {\tilde b_1} {\tilde b_1} \to t {\bar t} W^+ W^- \tilde��^0_1 \tilde��^0_1$ may be necessary.

43 pages, 18 figs