The magnetic and transport properties of compounds La2/3Ca1/3Mn1-xTixO3(0x0.3) have been investigated. The substitution of Ti for Mn suppresses the ferromagnetism and metal conduction and increases magnetoresistance dramatically. In the case of low doping (x0.04), substituting Ti for 1% Mn lowers Curie temperature TC and metal-insulator transition temperature Tp by about 31 and 26.5K respectively. The magnetic spontaneous state becomes cluster glass state for the compound with x=0.06, and turns into spin-glass state for the compound with x=0.20. The magnetic dilution and the local lattice distortion due to the introduction of Ti are suggested to explain the experimental results.