Abstract: Cheap micron grade CaCO₃ whisker was incorporated into the millimeter grade steel fiber and polyvinyl alcohol (PVA) fiber hybrid fiber reinforced cement-based composites (HyFRCC). The influence of CaCO₃ whisker on mechanical behaviors, failure pattern and size effect of thin HyFRCC slabs was studied. The micro morphology of the composites was observed using SEM. The experimental results show that the thin slabs demonstrate good flexural performance, better pseudo strain hardening and multiple cracking behaviors than beams with addition of whisker. And the HyFRCCs including CaCO₃ whisker are more efficient in reducing the size effect sensitivity on flexural strength. The micromorphology observation verifies that the hybrid fiber system incorporating CaCO₃ whisker can inhibit the crack propagation at different scales. The study indicates that the steel fibers and PVA fibers can be replaced partly with cheap CaCO₃ whiskers to produce HyFRCC, which shows good adaptability to fabricate slab element. And the dual goals of mechanical performance optimization and economy efficiency increase are both achieved.