Abstract: The influence law of different BF content and length on the strength of low-heat cement concrete at different ages was systematically explored, which provided a basis for improving the strength of low-heat cement concrete at early ages. BF content was set as 0.0%,0.1%,0.2% and 0.3%, length was set as 12 mm and 24 mm, and curing age was set as 3 d, 5 d, 7 d, 14 d and 28 d. And the influence law of BF content and length on compressive strength of low-heat cement concrete of different ages was obtained. The results showed that the strength performance of low-heat cement concrete can be improved by BF of different lengths and contents with the maximum increase of 20.47%. There are significant differences in the strength effect of BF fiber content and length at different ages. Except for 3 d age, the compressive strength at other ages shows a trend of first increasing and then decreasing with the increase of 12 mm BF content, and the peak compressive strength content is 0.2%. Except for the 28 d age, the compressive strength shows an increasing trend with the increase of 24 mm BF content, while the compressive strength at 28 d age shows a trend of first increasing and then decreasing with the increase of 24 mm BF content, and the turning point content is 0.1%. Under the condition of the same BF content and length, BF has a more significant effect on the compressive strength of low-heat cement concrete at short age than that at long age. BF length of 12 mm and the content of 0.2% are recommended.