A method for measuring wood density of live timber, comprising: measuring a diameter of a test part of the live timber at a first height from a ground surface; transmitting and receiving microwave in a preset frequency range in air at a first distance greater than the diameter, and measuring a first ratio of a transmitted microwave signal to a first received microwave signal at different frequencies; transmitting microwave in the air at the first height so that microwave penetrates the test part of the live timber, receiving the microwave at the first distance from the microwave transmitting position, and measuring a second ratio of a transmitted microwave signal to a second received microwave signal at different frequencies, wherein, a dielectric constant and an attenuation constant of the live timber is calculated according to the first ratio, the second ratio and the diameter; a relationship is determined between the wood density of the live timber and the dielectric constant and the attenuation constant, and the wood density of the live timber is calculated according to the relationship, characterized in that: the relationship between the wood density of the live timber and the dielectric constant and the attenuation constant comprises: ρ = aε + b 1 − α − q 100 p wherein, ρ is the wood density of the live timber, ε is the dielectric constant of the live timber, α is the attenuation constant of the live timber, and a, b, p, q are pre-calibrated parameters related to tree species of the live timber. measuring a diameter of a test part of the live timber at a first height from a ground surface; transmitting and receiving microwave in a preset frequency range in air at a first distance greater than the diameter, and measuring a first ratio of a transmitted microwave signal to a first received microwave signal at different frequencies; transmitting microwave in the air at the first height so that microwave penetrates the test part of the live timber, receiving the microwave at the first distance from the microwave transmitting position, and measuring a second ratio of a transmitted microwave signal to a second received microwave signal at different frequencies, wherein, a dielectric constant and an attenuation constant of the live timber is calculated according to the first ratio, the second ratio and the diameter; a relationship is determined between the wood density of the live timber and the dielectric constant and the attenuation constant, and the wood density of the live timber is calculated according to the relationship, characterized in that: the relationship between the wood density of the live timber and the dielectric constant and the attenuation constant comprises: ρ = aε + b 1 − α − q 100 p wherein, ρ is the wood density of the live timber, ε is the dielectric constant of the live timber, α is the attenuation constant of the live timber, and a, b, p, q are pre-calibrated parameters related to tree species of the live timber. the relationship between the wood density of the live timber and the dielectric constant and the attenuation constant comprises: ρ = aε + b 1 − α − q 100 p wherein, ρ is the wood density of the live timber, ε is the dielectric constant of the live timber, α is the attenuation constant of the live timber, and a, b, p, q are pre-calibrated parameters related to tree species of the live timber.