Bubble-particle impact in flotation is usually approximated to the particle approaching against a plane gas-liquid interface. In this paper we theoretically re-investigate this interaction and deal with its non-linear problems. It is evident that the restoring force is a non-linear ＇mixed＇ function of the transition angle and the maximum depth of the deformed gas-liquid interface. This ＇mixed＇ expression makes analytical prediction of collision time impossible. In this paper, the restoring force is approximately predicted in terms of the maximum depth of the deformed gas-liquid interface. Dynamics of the impacting particle can be described solely by the maximum depth, The non-linear differential equation describing the particle oscillation is analytically solved using an approximation method. Collision time is analytically predicted. Two characteristic dimensionless parameters, viz., the Bond number and the Weber number of collision, are introduced to describe the impact interaction. A critical analysis of the so-called effective mass effect on collision time is performed and indicates that the effect of oscillation effective mass on collision time is small and can be ignored. The theoretical collision time model presented in this paper is based on the following parameters: the particle radius and the particle density, the density and viscosity of the liquid phase, and the tension of the gas-liquid interface.