Sericite schist particles are easy to disintegrate. Their performance can decay and weaken easily under long term wet-dry cycle effects. Both California bearing ratio (CBR) test and resilient modulus test (MD) are carried out on sericite schist particles with different initial maximum sizes. The strength variable characteristic is gained. Meanwhile, the paper reveals the interior disintegrated mechanism joined with particle size distribution curves. The results show that sericite schist particles don’t disintegrate obviously any further after they are subjected to more than 10 times wet-dry cycles. Moreover, they disintegrate rapidly if their particle sizes are greater than 10 mm. They disintegrate slowly if their particle sizes are less than 10 mm. The initial maximum particle size ranges corresponding to the strength peak value are 5-10 mm and 10-20 mm for CBR test and MR test, respectively. Hence, the initial maximum particle size of 10 mm could be recommended as controlled size for using sericite schist particles as subgrade fills.