In the production process, the asphaltene precipitation (AP) and deposition can not only,inflict damage On reservoir stratum but also lead to the shut-in of the well and incur the extra cost of remediation. In this study, the phase behavior of asphaltenes in live oil under high-temperature and high-pressure conditions was determined using a modified solid (asphaltene) deposition laser detection apparatus The test accuracy was greatly improved as a result Of the increase of the laser power, The phase behavior of asphaltenes in live oil, which was characterized by the heavy components and dark, color, was evaluated The oil sample was from the Fahliyan oilfield in Iran, which is suffering big AP problems. In addition, the Values of the bubble point pressure (BPP) obtained by this apparatus have proven to be well-matched with that measured by the constant composition experiment (CCE) test Moreover, the equation of state (EOS) of the asphaltene and crude oil obtained by the fitting curve can be used to further optimize the mathematical prediction model. Furthermore, the phase diagram is completed in conjunction with the P-T curve to predict the deposition location of asphaltene in the well For the example well, the predicted results at the depth of 1930 m are almost comparable to the results of the actual production process at the depth of 1845 m, which only has a difference of 2.1%. Accordingly, the addition of chemical inhibitors is recommended as an effective method to reduce the risk of AP in the example well.