In this research, the formulations for chitosan and chitosan-alginate beads containing pendimethalin were developed and explored for their control release ability. The entrapment of pendimethalin in chitosan beads was investigated. The release rate of pendimethalin loaded chitosan was not satisfactory. To increase the release rate of pendimethalin, alginate as a good water soluble polymer and can act as hydrogel was used in combination with chitosan. The study showed that chitosan and chitosan-alginate beads had very low release rates. To solve this problem, alginate beads were prepared to control the release of pendimethalin. During drying process of making beads, the initial spherical shape was lost and shrinkage occurred. The beads were eventually prepared using alginate and starch. SEM images of beads suggested the formation of spherical beads. FTIR confirmed chemical stability of pendimethalin in alginate-starch beads. A series of beads with different compositions were prepared by varying type of starch, ratio of alginate, starch, concentration of CaCl₂ and immersion time. When the concentration of CaCl₂ and immersion time were increased, the swelling and release rate decreased. The mechanism of alginate-starch beads was believed to release pendimethalin at the beginning once the beads were swelled and then eroded together with pendimethalin release. The study showed that alginate-starch beads had sufficient release of pendimethalin. The efficacy study confirmed that alginate-starch beads could be used to control the germination of weeds.