Porous latex particles have been of increasing interests for scientific and industrial entrepreneurs due to their promising applications in diverse fields. In this paper, porous latex particles consisting of St-MMA-AA(or MMA) were successfully prepared through 2 step seeded emulsion polymerization followed by alkali/acid treatment. Influences of AA(orMAA) content, and of the crosslinking agent on hollow formation inside the particles were studied. Results showed that a minimum AA content must be appropriate AA content, hollows were well formed and particle volume was significantly expanded; at a higher AA content, hollows were also observed, but particle size expansion was reduced and even particle contraction appeared, crosslinking of latex is effective to prevent oarticles from contraction. Results were discussed based on the mechanism of hollow formation.