Sargassum crassifolium is a brown seaweed which produce alginate that spread in the Indonesian’s ocean and often use in food industrial. Alginate has heat stable better than gelatin, therefore it can raise up the melting point of product. Carbohydrates in alginate and protein gelatin can make gel together, so it can be more synergy. Gel of alginate and gelatin can be combined to produce jelly candy. The objective of this research is to extract and characterize alginate from Sargassum crassifolium and to determine the best ratio and type of alginate to produced jelly candy with the best characteristic. Alginate was extracted from extraction of Sargassum crassifolium with Na2CO3 10% in 60 o C for 90 minutes. The extraction was produced acid and can be converted to sodium and potassium alginate through ion exchange. The ratio between alginate and gelatin were 1:1 ; 1:1,5 ; and 1,5:1. Alginic acid, sodium alginate, and potassium alginate will be combined with gelatin. The best jelly candy was made from use of sodium alginate with ratio 1:1,5 which compare with jelly commercial. The characteristic of the best jelly candy were pH 5,73 ; gel strength 48,6 g.cm ; melting point 45,5 C ; gelling point 21,50 C ; L score 38,54 ; a score 5,04 ; b score 14,86 ; moisture content 21,98% ; ash content 0,17% ; sucrose content 38,94% ; and total reducing sugar 24,52%.