  After considering the effects of negative feedback on the process of star
formation, we explore the relationship between star formation process and the
associated feedback, by investigating how the mechanical feedback from
supernovae(SNe) and radiative feedback from luminous objects regulate the star
formation rate and therefore affect the cosmic reionization.Based on our
present knowledge of the negative feedback theory and some numerical
simulations, we construct an analytic model in the framework of the Lambda cold
dark matter model. In certain parameter regions, our model can explain some
observational results properly. In large halos(T_vir>10000 K), both mechanical
and radiative feedback have a similar behavior: the relative strength of
negative feedback reduces as the redshift decreases. In contrast, in small
halos (T_vir<10000 K$) that are thought to breed the first stars at early time,
the radiative feedback gets stronger when the redshift decreases. And the star
formation rate in these small halos depends very weakly on the star-formation
efficiency. Our results show that the radiative feedback is important for the
early generation stars. It can suppress the star formation rate considerably.
But the mechanical feedback from the SNe explosions is not able to affect the
early star formation significantly. The early star formation in small-halo
objects is likely to be self-regulated. The radiative and mechanical feedback
dominates the star formation rate of the PopII/I stars all along. The feedback
from first generation stars is very strong and should not be neglected.
However, their effects on the cosmic reionization are not significant, which
results in a small contribution to the optical depth of Thomson scattering.
