Abstract: natural gas Z-factor is an important physical parameter in engineering calculation, and it is also a basic value in gas reserves calculation and dynamic analysis. Aimed at the current engineering calculations using a single computational model of natural gas deviation factor, whose pressure range is small and precision is low, and iterative calculations is needed, a high-precision analytical calculation model of natural gas Z-factor with whole pressure and temperature range have been set up. This model is suitable for pressure of 0~140 MPa and easier to be calculated by hand or computer. Difference and error analysis shows that, in most cases, the relative error is below 1%, thus LXF-RMP model is more precise in whole pressure and whole temperature range.