Abstract: The test values of MOR & MOE of bamboo particle composite board (abbreviated to BPCB) with symmetrical structure show no relationship with the width of specimens. On the basis of this conclusion, the bending rigidity characteristic and the stress distribution of BPCB Under perpendicular load are studied by simulating beam method. And a series of theoretical evaluating models of MOR and MOE for BPCB are deduced. This paper also advances a theory of optimilizing the structure of BPCB. By analysing the rupture modes of the BPCB specimens at different spans, the rupure criteria of BPCB in use are developed.