Abstract: The uniaxial st rain cyclic characteristics and ratcheting behavior of T6-t reated SiC_P / 6061Al alloy composites were experimentally studied at high temperature (300 ℃) . The cyclic sof tening/ hardening feature and ratcheting behavior of the composites containing two kinds of particulate volume f ractions were discussed under differentloading conditions at high temperature. It is shown that the particulate reinforced metal mat rix composites showsimilar st rain cyclic characteristics and ratcheting behavior to those of metals on a macro-scale. Namely , the ratcheting also occurs in the composites under asymmet rical cyclic st ressing , and the ratcheting st rain increases with theincrease of the st ress amplitude and mean st ress ; however , the addition of SiC particulates into the mat rix increasesthe resistance of the composites to ratcheting , and the ratcheting st rain decreases with the increase of the volumef raction of SiC particulates ; at 300 ℃, the ratcheting has great time2dependence , i. e. , the ratcheting st rain dependsgreatly on the st ressing rate and hold-time at peak st ress , and an interaction of creep and ratcheting is remarkable.The effect s of microst ructure features of the composite , loading condition and time on the ratcheting should be wellconsidered when t rying to const ruct a constitutive model to describe such ratcheting.