Pneumatic shapemeter is specialized tension sensor that is used for foil flatness online realtime detection and shape control. The operating principle and characteristic of the pneumatic shapemeter were introduced, the performance of the pneumatic shape was studied by experiment. These experiments included the relation of pressure taps differential pressure and load under the condition that different air source pressure was imposed on pneumatic shapemeter ,the effect of air source pressure on differential pressureload sensitivity of measuring roller，the minimum working air source pressure of the pneumatic shapemeter. The results show that the designed pneumatic shape has a well detection characteristic and is suitable for detecting the strain of aluminum foil under a smaller load.