  In the little higgs scenario, several coupling constants are related to each
other to guarantee the stability of the higgs boson mass at one-loop level.
This relation is called the little higgs mechanism. We discuss how accurately
the relation can be tested at future $e^+e^-$ colliders, with especially
focusing on the top sector of the scenario using a method of effective
lagrangian. In order to test the mechanism, it is important to measure the
Yukawa coupling of the top partner. Higgs associated and threshold productions
of the top partner are found to be the best processes for this purpose.
