An integrated ultra-high-resolution ratio-metric wavelength monitor (RMWM) with compact size based on slope tunable Fano resonance is demonstrated on silicon. The Fano resonance is generated by adding an asymmetric microring inside and coupling with the outer ring to produce a nonlinear phase shift. The slope tunability is achieved by controlling the microheaters to adjust the phase condition. Two asymmetric embedded microring resonators (AEMR) are functioned as edge filters and designed to achieve an "X-type" spectral response in a particular wavelength range. An ultra-high resolution of 0.8 pm in a 0.47 nm wide wavelength range is experimentally demonstrated. This device could be applied in on-chip high-sensitivity wavelength monitoring sensing.