Reliability data which come from the main testing phases of product developing course were supposed to be varied population\|environment data. Based on varied population-environment data, an integrated evaluation model of reliability was established. This model used Duane model of reliability growth as foundation, and introduced environment conversion factors under different testing conditions. An engineering method was recommended to solve the environment conversion factors. Based on the model, an integrated method and steps to evaluate product's reliability were determined. An example using practice data was presented.