A method for predicting outdoor three-dimensional space signal field strength by extended COST-231-Walfisch-lkegami propagation model, comprising: establishing a three-dimensional scene model from a transmitting base station to a predicted region space; performing an on-site measurement according to a certain resolution in a prediction region and recording wireless signal strength information at a height of 1 m above the ground; acquiring a vertical cross section between the transmitting base station and a receiving point at a height of 1 m above the ground, and acquiring therefrom an average roof height, an average street width, an average between-building space, a transmitting base station height, a receiving point height, a transmitting base station transmitting power, a transmitting base station transmitting signal frequency, a distance between the transmitting base station and a measurement point, and an angle between an incident direction of a base station direct wave and a direction of a street to which the measurement point belongs; predicting a reception signal strength at the measurement point in a calculation formula of a COST-231-Walfishch-Ikegami propagation model; characterized in that the method comprises: correcting the COST-231-Walfishch-Ikegami propagation model of the measurement point according to an error Δ between measured data and a prediction result; acquiring a vertical cross section between the transmitting base station and a receiving point at other height of the measurement point, and filtering therefrom buildings outside a Fresnel circle to re-acquire the average roof height, an average street width and an average between-building space, a transmitting base station height, a receiving point height, a transmitting base station transmitting power, a transmitting base station transmitting signal frequency, a distance between the transmitting base station and a measurement point, and an angle between an incident direction of a base station direct wave and a direction of a street to which the measurement point belongs; and calculating a reception signal strength at other height of the measurement point according to the corrected COST-231-Walfishch- Ikegami propagation model. establishing a three-dimensional scene model from a transmitting base station to a predicted region space; performing an on-site measurement according to a certain resolution in a prediction region and recording wireless signal strength information at a height of 1 m above the ground; acquiring a vertical cross section between the transmitting base station and a receiving point at a height of 1 m above the ground, and acquiring therefrom an average roof height, an average street width, an average between-building space, a transmitting base station height, a receiving point height, a transmitting base station transmitting power, a transmitting base station transmitting signal frequency, a distance between the transmitting base station and a measurement point, and an angle between an incident direction of a base station direct wave and a direction of a street to which the measurement point belongs; predicting a reception signal strength at the measurement point in a calculation formula of a COST-231-Walfishch-Ikegami propagation model; characterized in that the method comprises: correcting the COST-231-Walfishch-Ikegami propagation model of the measurement point according to an error Δ between measured data and a prediction result; acquiring a vertical cross section between the transmitting base station and a receiving point at other height of the measurement point, and filtering therefrom buildings outside a Fresnel circle to re-acquire the average roof height, an average street width and an average between-building space, a transmitting base station height, a receiving point height, a transmitting base station transmitting power, a transmitting base station transmitting signal frequency, a distance between the transmitting base station and a measurement point, and an angle between an incident direction of a base station direct wave and a direction of a street to which the measurement point belongs; and calculating a reception signal strength at other height of the measurement point according to the corrected COST-231-Walfishch- Ikegami propagation model. correcting the COST-231-Walfishch-Ikegami propagation model of the measurement point according to an error Δ between measured data and a prediction result; acquiring a vertical cross section between the transmitting base station and a receiving point at other height of the measurement point, and filtering therefrom buildings outside a Fresnel circle to re-acquire the average roof height, an average street width and an average between-building space, a transmitting base station height, a receiving point height, a transmitting base station transmitting power, a transmitting base station transmitting signal frequency, a distance between the transmitting base station and a measurement point, and an angle between an incident direction of a base station direct wave and a direction of a street to which the measurement point belongs; and calculating a reception signal strength at other height of the measurement point according to the corrected COST-231-Walfishch- Ikegami propagation model.