The invention relates to a collecting agent and application thereof to fine fraction gold ore flotation. According to one kind of application, a cross-linking agent Sac100 serves as the collecting agent, the cross-linking agent in this kind of application comprises the cross-linking agent Sac100 and kerosene, and the mass ratio of the cross-linking agent Sac100 to xanthate is 1.5:(6-8); the cross-linking agent also comprises polyethylene glycol, and the mass ratio of the cross-linking agent Sac100 to polyethylene glycol to xanthate is 1.5:(1-2):(6-8). According to the second kind of application, the collecting agent is applied to fine fraction gold ore flotation. By using the collecting agent, the recovery rate of -400 mesh gold ore can be increased by 5 percent points on average.