Based on literatures and test results in our lab., some design principles of a UF adhesive arepresented in this paper as follows: 1) The end F/U mole ratio of the UF resin has to be 1.40-1.20: 1.0 for good bonding strength of panels bonded with resins; 2)In order to decrease the release level of formaldehyde from wood-based panels below 10mg/100g (perforator method), the free urea in the resin should be more than 10.0% of all urea used; 3) The cycle compounds of urea, such as Uron and triazine, are introduced into molecules of the UF resin, it is preferable that the cyclecompounds are about 10% of all urea added There are 3 UF resins cooked according to the principles for particleboard and MDF uses, all the formaldehyde release levels are less than 10mg/100g, and the physical and mechanical properties are better than those of Chinese national and enterprise standards