A new compact optical Fano filter suitable for biological sensing is proposed, which patterns photon crystal in single crystalline silicon nanomembranes (SiNMs) and transferring onto transparent glass substrates. The effects of air hole size and silicon thickness on the transmission characteristics of new filter are numerically investigated by using three-dimensional finite-difference time-domain (FDTD) technique, the spectral response is also studied by back-filling bio-liquid. The results show that the dip wavelength will shift toward longer wavelength by either reducing air hole radius or filling bioliquid. The number of dips will increase with the increase of silicon thickness. The size of proposed filter can be less than 1 mm². This work has been partly Supported by the Research Program of Science and Technology of Fujian Education Office of China (No.JA08183 and JA081878)