The mutual energy-exchange interactions in two orthogonally polarized components of vector dark soliton, which is automatically formed in a normal-dispersion fiber laser cavity in the presence of reverse saturable absorption, and dissipative cavity effects, had been theoretically and numerically investigated. Under specific cavity parameters, a vector dark soliton with periodic coherent energy exchange could be formed and well described by a semianalytic method. The multiple vector dark solitons with energy exchange were also demonstrated by combining gain bandwidth and a reverse saturable absorption effect.