OBJECTIVES:  “Cancer Prevention and Treatment Policy” was launched by Health Promotion Administration in 2010 in Taiwan. Its strategy was to increase the coverage of cancer screening and  pay more emphasis on cancer treatment than on cancer prevention. This study aims to evaluate whether the implementation of the policy can improve the early diagnosis of cancer. METHODS: The data was obtained from Taiwan Cancer Registry Database between 2008 to 2011. This study employed a quasi-experimental design and use a difference-in-differences (DID) analysis to identify the net effect of the policy. The colorectal, oral, cervical and breast cancer which enrolled into the policy were identified as “case group”, and then constructed a “control group”, which were not affected by the program and with four other types of cancers: esophagus, stomach, bladder and prostate cancer. Because the policy was enacted in January 2010, this study defined the pre-intervention period from January 2008 to December 2009 and the post-intervention period from January 2010 to December 2011. RESULTS: There were 152,515 patients identified from 2008 to 2011 for 8 cancer types. For 115,810 patients in case group, those who diagnosed during post-intervention period (64.33%) were more likely to be diagnosed at an early-stage of cancer than those who diagnosed during pre-intervention period (63.47%). The proportion of patients diagnosed increased by 0.86% after policy intervention. For 36,705 patients in control group, those who diagnosed during post-intervention period (50.04%) were more likely to be diagnosed at an early-stage of cancer than those who diagnosed during pre-intervention period (49.90%). The proportion of patients in control group diagnosed increased by 0.15% after policy intervention. Comparing the change of policy intervention, we found that the difference between two groups was 0.71% fewer. CONCLUSIONS: The Cancer Prevention and Treatment Policy in Taiwan can help to improve the early diagnosis of cancer .