SQUID bootstrap circuit (SBC) is a SQUID direct readout operating in the voltage bias mode. It consists of two branches connected in parallel: SQUID-inductance L-a branch and inductance L-b-resistance R-b branch. Its bias voltage is connected to the input terminal of preamplifier. In the SBC the voltage noise from the preamplifier creates the current noise which can be modified by the parameters. Based on the equivalent circuit for SBC and its network equations we studied its characteristics and the effect of parameters on current noise due to biased voltage noise by numerical simulation. Results suggest that SBC current noise can be effectively reduced by modifying parameters, in optimal condition the current noise can be totally suppressed. The effect of resistance R-b on the excess noise is discussed. (C) 2012 Published by Elsevier B.V. Selection and/or peer-review under responsibility of the Guest Editors.