Abstract: This paper reviews firstly method for treating low speedrarefied gas flows: the linearized Boltzmann equation method , the LaticeBoltzmann method (LBM), the Navier-Stokes equation plus slipboundary conditions and the DSMC method, and discussed thedifficulties in simulating low speed transitional MEMS flows, especiallythe internal flows. In particular, the present version of the LBM is shownunfeasible for simulation of MEMS flow in transitional regime. Theinformation preservation (IP) method overcomes the difficulty of thestatistical simulation caused by the small information to noise ratio forlow speed flows by preserving the average information of the enormousnumber of molecules a simulated molecule represents. A kind ofvalidation is given in this paper. The specificities of the internal flows inMEMS, i. e. the low speed and the large length to width ratio, result inthe problem of elliptic nature of the necessity to regulate the inlet and theoutlet boundary conditions that influence each other. Through theexample of the IP calculation of the microchannel (thousandsmicrometers long) flow it is shown that the adoption of the conservativescheme of the mass conservation equation and the super relaxationmethod resolves this problem successfully. With employment of the samemeans the IP method solves the thin film air bearing problem intransitional regime for authentic hard disc write/read head length(L=1000 micrometers) and provides pressure distribution in fullagreement with the generalized Reynolds equation, while before this theDSMC check of the validity of the Reynolds equation was done only forshort (L=5 micrometers) drive head. The author suggests degenerate theReynolds equation to solve the microchannel flow problem in transitionalregime, thus provide a means with merit of strict kinetic theory for testingvarious methods intending to treat internal MEMS flows in transitionalregime.