The beneficial effects of unfractionated heparin and low molecular weight heparin on cancer progression have been reported. In the study, the effect of dalteparin on pulmonary adenocarcinoma A549 cell line was observed in vitro. Our experiments revealed that: (1) dalteparin can inhibit the cell viability dose-dependently and time-dependently; (2) dalteparin can arrest the A549 cells in G(1) phase and induce them to early apoptosis; (3) dalteparin exerts its effects through p21(WAF1) and p27(KIP1) proteins; and (4) the changes of p21(WAF1) and p27(KIP1) proteins caused by dalteparin occurred at posttranscriptional levels.