Taking Rhododendron calophytum Franch.， R. molle （Blume） G. Don， R. delavayi Franch.， and R. decorum Franch. as research objects， effects of corncob biochar and rice husk biochar extracts with biochar water ratios of 1∶30， 1∶15， and 1∶7.5 on their seed germination characteristics were compared. The results show that compared with the control （deionized water）， seed germination rate and germination index of R. calophytum， R. molle， and R. delavayi in corncob biochar extract treatment group with biochar water ratio of 1∶30 and three rice husk biochar extract treatment groups all increase significantly， and their germination time lag is shortened； seed germination rate of the three species in corncob biochar extract treatment groups with biochar water ratios of 1∶15 and 1∶7.5 decreases. In addition， seed germination rate of three species in rice husk biochar extract treatment groups with biochar water ratios of 1∶15 and 1∶7.5 is evidently higher than that in corncob biochar extract treatment groups with the same biochar water ratio. Overall， corncob biochar and rice husk biochar extracts can inhibit seed germination of R. decorum， and the higher the biochar water ratio， the stronger the inhibitory effect. In conclusion， there are differences in effects of corncob biochar and rice husk biochar extracts on seed germination of species in  Rhododendron Linn.， and there is interspecific difference in influence effect.