Abstract: This paper deals with the selection and calculation of vibrational parameters of the vibrating seed harvester, the frequency and acceleration range at which the ripe cones and seeds of Chinese fk (Cunninghamia Lanceolate Hook) and masson pine (Pinus Mossoniana Lamb.) fell best, the determination of the nature frequency, the elastic modulus and damping coefficient and the advancement of simplified mechanical model of trees. The author has deduced a method of vibrational calculation and compared it with the measured value. The main results of this study could be summed up as follows:1. The frequency ranges from 5HZ to 100HZ. The optimum frequency of Chinese fir is from 70HZ to 80HZ and that of Masson pine from 50HZ to 60HZ. The range of the acceleration is above 5g.2. The elastic modulus of Chinese fir tree is 58900kg/cm2 and that of Masson pine 51600kg/cm2, with damping coefficent from 0.23 to 0.36.3. Vibration of a tree trunk can be simplified as lateral vibration of a uniform cantilevered beam with infinite number of degrees of freedom. The difference in the first frequency between calculation and actual measured value is about 10%.4. Under the condition of 80HZ and an acceleration of log, the exciting force needed ranges from 50kg to 500kg to excite a cedar tree with its diameter from 10cm to 25cm and height from 6m to 15m.5. The energe dissipated for vibrating a tree is little, so much power can be saved.