In this peper

we stier the isonetric deformations of the sparelik. and timelike surfaces in 3dimensional Minkowski space R2.1 preserving the mean curvature function

which are

called H.deformation first

we give a necessary and sufficient .condition for the existence of the H-deformable spacelike or tirnelike immersion in R2.1

Next

we discuss the H-deformations of the spacelike and'timelik. surfaces with constant'mean curvature. Moreover

we offer twocharacterizations of the H-deformable spacelike or timelike surface in R2

1. At last

we give aexample of H-deformation of flat timelike surface.