Hydrogenated amorphous silicon (a-Si:H) deposited using plasma-enhanced chemical vapor deposition (PECVD) is used as the passivation layer for p-type multi-crystalline black silicon (p-mc-b-Si) wafers. The effects of deposition conditions on passivation quality are investigated. The optimized a-Si:H passivation layer enables the best surface passivation with an implied open-circuit voltage (iV(oc)) of 710 mV, which is better than other conventional passivation materials. The excellent passivation quality possibly resulted from that the activated hydrogen from a-Si:H at similar to 200 degrees C was able to passivate both surface defect states and bulk trap states of p-mc-b-Si effectively. Moreover, an additional SiNx capping layer helps to reduce reflectance significantly and to keep passivation quality. This work suggests that b-Si passivated by a-Si:H/SiNx stack film shows potential for various optoelectronic devices that requires both excellent optical anti-reflectance and surface passivation.