  In present report we review some preliminary results of investigation of
higher orders of mean-field expansion for Nambu--Jona-Lasinio model. We discuss
first results of investigation of next-to-next-to-leading order of mean-field
expansion equations for four-quark and three-quark Green functions. We have
considered equations for Green functions of Nambu--Jona-Lasinio model in
mean-field expansion up to third order.
