Motivated by the recent LHCb observation of CP violation in charm, we study CP violation in the charmed baryon decays. A simple method to search for the CP violation relations in the flavor SU(3) limit, which is associated with a complete interchange of d and s quarks, is proposed. With this method, hundreds of CP violation sum rules in the doubly and singly charmed baryon decays can be found. As examples, the CP violation sum rules in two-body charmed baryon decays are presented. Some of the CP violation sum rules could help the experiment to find better observables. As byproducts, the branching fraction of $$\Xi ^+_c\rightarrow pK^-\pi ^+$$ Ξc+→pK-π+ is predicted to be $$(1.7\pm 0.5)\%$$ (1.7±0.5)% in the U-spin limit and the fragmentation–fraction ratio is determined to be $$f_{\Xi _b}/f_{\Lambda _b}=0.065\pm 0.020$$ fΞb/fΛb=0.065±0.020 using the LHCb data.