In this study, the burning behaviors of three species of plantation wood （Cunninghamia lanceolata, Pinus massoniana and Populus euramericana cv.‘I-214’）, respectively treated with two retardants, boride （H,3,BO,3,∶Na,2,B,4,O,7,=1∶1 ） and ammonium primary phosphate, were all tested by cone calorimeter. The fire retarding effect of these retardants was evaluated by comparing the burning indexes of these three treated wood species, such as ignition time, mass loss rate, heat release rate, total heat released and total smoke production. It was found that the boride fire-retardant had poorer results in inhibiting ignition, heat release and mass loss in wood than the ammonium primary phosphate, but it was more effective than the latter in hindering smoking. These differences were analyzed and related with the retarding mechanisms of the two retardants.