Process 1/4 cup preserves and next 5 ingredients in a food processor 30 seconds to 1 minute or until smooth. With processor running, pour oil through food chute in a slow steady, stream, processing until smooth. Transfer to a 2-cup measuring cup or small bowl, and stir in remaining 2 Tbsp. pear preserves.
Place arugula in a large serving bowl. Top with pears, blue cheese, and walnuts. Drizzle with vinaigrette.