Based on the characteristic of a long road tunnel, it is necessary to use combination methods to forecast the strata condition ahead, such as the combination of advanced geological drilling, GPR nd TSP. But each method has its own advantages, disadvantages and geo-conditions. The forecasting results by using a single method may be conflicted with other methods. In this paper, the fuzzy synthetic judgement method is adopted to analyze the different geological forecasting results. In conclusion, the location of surrounding rock, the rock strength, the joints and water condition can be determined. Moreover, the relationship between the strata properties and the main characteristic parameters of each forecasting method is discussed as well. Finally the fuzzy synthetic judgement method is applied to a case, which shows that this synthetic method is accurate and reliable in road tunnel geological prediction.