Black humor plays a crucial role in fulfilling Langston Hughes's anti-racist purposes as an integral notion in his poetry. Accordingly, translation (s) of his poetry are to benefit from the same indexes on the basis of equivalent effect principle. On this account, 33 black-humor-rich poems of Hughes, translated by Ahmad Shamloo, Yaghma Golruee and Hassan Fayyad, were selected to be analyzed contrastively in search of black humor indexes in the target text (TT). Then they were all analyzed based on the six-leveled Knowledge Resources (KR) hierarchy, including Language (LA), Narrative Strategy (NS), Target (TA), Situation (SI), Logical Mechanism (LM) and Script Opposition (SO), proposed by Attardo and Raskin. The result demonstrated that all the levels remained approximately intact through the translation except the LA and SO which appeared the most vulnerable. That is, mistranslation at the language level of a linguistic chunk which has a direct implication to specific scripts of black humor leads to the loss of black humor indexes in the TT.