In this paper, a porous silicon-calcium fluoride hybrid plasmonic waveguide (PS-CaF ₂HPW) with an asymmetric silver film is studied. The PS-CaF ₂HPW is composed of a PS strip waveguide deposited with asymmetric CaF ₂and Ag thin film layers on an SiO ₂substrate. In the mid-infrared (MIR) region, the mode characteristics and waveguide sensitivity of the mode in the PS-CaF ₂HPW are simulated by using the finite element method (FEM). The results show that there are two fundamental modes (PM 1 and PM 2) with different polarization states in the PS-CaF ₂HPW. The real part of the effective refractive index (Re( n _eff )), transmission loss ( α), normalized effective mode field area ( A), quality factor ( FOM) and sensitivity ( S _wg) for each of the PM 1 and the PM 2 are studied and optimized. Moreover, the effect of temperature on the performances of the PS-CaF ₂HPW is also analyzed. Firstly, the mode field distributions calculated by the FEM indicate that the mode field energy for each of the PM 1 and PM 2 in the PS-CaF ₂HPW is mostly restricted to the PS layer and CaF ₂layer. Comparing with conventional dielectric waveguides, the mode field energy of the PS-CaF ₂HPW is well confined in the PS layer and CaF ₂layer. The geometric parameters of the PS-CaF ₂HPW are optimized by changing the geometric parameters ( W ₁, W ₂, and W ₃). When W ₁= 1500 nm, W ₂= 300 nm, W ₃= 70 nm, and the operating wavelength is ~3.5 μm, αand FOMare 0.019 dB/μm and 1594.99 for the PM 1, and αand FOM are 0.016 dB/μm and 1335.54 for the PM 2, respectively. Secondly, the waveguide sensitivity of the PS-CaF ₂HPW is analyzed. The results show that the size of PS layer has a great influence on the waveguide sensitivity. The waveguide sensitivity decreases with the size of the PS layer increasing. In addition, the PS-CaF ₂HPW has good temperature resistance. Moreover, temperature has almost no effect on Re( n _eff ), nor αnor Anor FOM nor S _wgin a temperature range from -40 K to 40 K. Finally, the fabrication tolerances of the PS-CaF ₂HPW are demonstrated, and the good properties are maintained in a size tolerance range from -10 nm to 10 nm. With the advantages in propagation property and loss reduction, the PS-CaF ₂HPW provides a feasible label-free biochemical sensing scheme and a method of polarization control devices.