According to the requirements of high-resolution spaceborne camera focusing mechanism, a dual readings multi-turn absolute encoder is designed. Accuracy and high-resolution glass plate is the first level absolute matrix optical code disc; metal plate with light weight and small size is the second level absolute matrix optical code disc which completes the count of the number of first level disc turns; double slit and double reading system to meet the circuit cold backup. The encoder can offer that resolution of 80″, accuracy between ± 100″, cylinder number is 16, its dimensions for φ 50 mm×50 mm, weight of 270 g. According to the requirements of identified spaceborne product, the function of encoder is verified through kinds of experiments. The experimental result shows that the encoder is stable, reliable and satisfies for the requirement of highresolution spaceborne focusing mechanism.