In a large saucepan or stock pot, combine the rhubarb, sugar and pineapple. Bring to a boil over medium-high heat. Boil for 10 minutes, stirring frequently. Jars can be sterilized at the same time.
After the rhubarb mixture has boiled for 10 minutes, remove from heat, and stir in strawberry flavored gelatin powder. Transfer to sterile jars, seal with lids, and process for 15 minutes in a boiling water bath. Allow jars to cool in a draft-free area. Refrigerate jars after seal has been broken.