The decays into two SU(6)-mesons from pp at 300-900 MeV/c and at rest are studied in a quark model. The decays due to two qq annihilation and one qq creation with the 3s1 vertex are extensively investigated. A reasonable description is obtained for the cross sections ofpp →π-π+ and K-K+. The backward peak in the pp →K-K+ angular distribution is discussed. Combined with the previous result on the quark rearrangement process, the gross features of the decay branching ratios both in flight and at rest are reproduced by the present scheme.