BACKGROUND:The study was conducted to compare the antifertility effectiveness and side effects of the copper/low-density polyethylene nanocomposite IUD (experimental group) and the copper T220C IUD (control group). STUDY DESIGN:One hundred females were randomly divided into two groups (experimental group and control group, n = 50 in each group). Clinical observation and comparative study were performed on the two groups for 12 months. RESULTS:Follow-up rate was 100% at the 12th month. In the experimental group and control group, the cumulative continuation rates were both 92.0 per 100 women at the 12th month and there was no difference between them (p > .05). The pregnancy rate, removal rate and expulsion rate were low with the difference being not statistically significant (p>.05). The most common side effects were excessive menstrual bleeding, spotting and pain. The rates of side effects were lower in the experimental group than in control group, especially during the initial 3 months after insertion with the differences being statistically significant (p < .05). CONCLUSION:The new design of the copper/low-density polyethylene nanocomposite IUD showed low pregnancy rate, high contraceptive efficacy and satisfactory acceptability. The study suggested that the TCu220C IUD also had high contraceptive efficacy, but had relatively more side effects.