This experiment was conducted to compare the effects of sodium selenite and selenium yeast on dynamic change of egg selenium content in laying hens. Two hundred and sixteen 30-week-old healthy Hy-Line Brown laying hens with a similar laying rate were randomly assigned to 3 groups with 6 replicates in each group and 12 laying hens per replicate. The laying hens in control group were fed a basal diet without adding selenium, while those in experimental groups were fed the basal diet supplemented with 0.30 mg/kg selenium in forms of sodium selenite and selenium yeast, respectively. Preliminary trail period was 14 days and experimental period was 56 days. The results showed as follows: 1) there were no significantly differences in the laying rate, average egg weight, average daily egg weight, average daily feed intake, the ratio of feed to egg, mortality, and egg quality on day 56 of the experiment among the 3 groups (P>0.05). 2) The egg selenium content in the group supplemented with selenium yeast was significantly higher than that in the group supplemented with sodium selenite and in the control group on day 3 of the experiment (P<0.05), and the egg selenium content in the group supplemented with sodium selenite was significantly higher than that in the control group after 14 days (P<0.05). On day 3, 5, 7, 14, 21, 28 and 56 of the experiment, the egg selenium content in the group supplemented with selenium yeast was 28.18%, 34.98%, 45.35%, 47.39%, 67.53%, 63.35% and 65.71%, respectively, and was significantly higher than that in the group supplemented with sodium selenite (P<0.05). As the experimental time increasing, the egg selenium content in the control group was decreased significantly (P<0.05), the egg selenium content in the group supplemented with sodium selenite showed a decrease and then increase trend (P<0.05), the egg selenium content in the group supplemented with selenium yeast was increased significantly (P<0.05). In conclusion, diet without adding selenium or supplemented with 0.30 mg/kg selenium in the form of sodium selenite and selenium yeast have no harmful effects on performance and egg quality in laying hens aged from 33 to 40 weeks. The selenium conversion rate and efficiency into egg of selenium yeast are significantly higher than sodium selenite. The addition of selenium in the diet can significantly increase egg selenium content, and the egg selenium content increases significantly as the experimental time increasing when the diet was supplemented with selenium yeast.