Deterministic random bit generator (DRBG) is an important building block for many cyber security systems. The secrecy of the seeds provides the basis for the security of DRBG. Periodic or dynamic reseeding is a good way of addressing the threat of the DRBG seeds, entropy input and working state being compromised over time. In this paper, the SRAM PUFs noisy cells will be used as the entropy source of DRBG. To this end, the most conservative estimate of min-entropy are tested under different temperature and reseeding times, confirm that the output of the entropy source can meet the requirements of DRBG in dynamic reseeding process. And then, min-entropy of authentication cells are tested in blocks, and discussed how to use it as nonce. Based on the tests above, this paper proposes a DRBG system which can reseed dynamically and monitor the entropy of entropy source in get entropy module online. This DRBG is implemented and tested in FPGA. 2250 times reseeding process random tests (by NIST SP 800-22 test suit) prove that this mechanism can be used in the cryptographic system.