A study by T-square sampling method was conducted to investigate importantplant species in Ban Pong Forest, Sansai district, Chiang Mai province by estimation of theirnumber and density, and testing of their random distribution. The result showed that, therewere 14 kinds of important plant species, viz. Dipterocarpus tuberculatus Roxb., Shoreaobtuse Wall. exBlume, Bridelia retusa (L.) A. Juss, Derris scandens Benth., Thysostachyssiamensis, Parinari anamense Hance, Vitex pinnata L.f., Canarium subulatum Guill.,Litsea glutinosa C.B.Roxb., Alphonsea glabrifolia Craib., Pueraria mirifica, Vaticastapfiana van Slooten, Walsura robusta Rox. and Dipterocarpus alatus Roxb. By far,Dipterocarpus tuberculatus Roxb was greatest in number and density, and all of the specieshad random distribution, except Walsura robusta Roxb and Dipterocarpus alatus Roxb