The effect of added polysaccharides on the phase behavior of (tobacco mosaic virus) TAW suspension has been investigated from experimental and computer simulation points of view. The addition of chondroitin sulfate (Chs) brings two interesting phenomena: (1) Chs induces aggregations of TMV particles at very dilute TAW concentration (enhancement of depletion interaction) and (2) the inter-rod distance in the TMV aggregates depends on the Chs concentration. The chain rigidity and electrostatic interaction between colloidal rod particles are responsible for the observed phenomena.