Determining the free shrinkage of U HPC is an important basis for analyzing the shrinkage effect of steel UHPC composite bridge deck.Therefore，based on the UHPC materials to be used in a project，three batches of UHPC free shrinkage specimens were made，and three specimens were made in each batch.By testing the strain and temperature of specimens during curing，the free shrinkage strain-age curve and temperature-age curve of UHPC were obtained.The development and variation law of UHPC shrinkage strain are discussed.Based on the experimental results，the equivalent time is introduced on the basis of Arrhenius empirical formula，and a modified model of free shrinkage is proposed.Finally，based on the regression analysis of the test results，the coefficients of the modified model are obtained.According to this discussion，the corresponding theoretical UHPC shrinkage stress calculate formula is obtained.The results show that the shrinkage from time zero to the point that temperature rise to 90 ℃ accounts about 42% of the total shrinkage during steam curing，and then the free shrinkage developed to more than 95% of the total shrinkage during steam curing within 48 hours after steam curing with 90 ℃.and the shrinkage strain curve will gradually stabilize during this period.And under the equivalent sealing curing condition of 20 ℃，the free shrinkage of UHPC will be basically completed about 40 days after time zero.