Zn1-xCdxSe epitaxial growth by molecular beam epitaxy (MBE) on the GaAs (110) surface cleaved in ultra high vacuum (UHV) was investigated. The growth mode of Zn1-xCdxSe on GaAs (110) was not a simple Stranski-Krastanow type. At initial growth stage, growth mode was two-dimensional type. However, as the growth proceeds three-dimensional island growth and two-dimensional growth modes compete. As a result, two kinds of structures were spontaneously formed on the surface, pyramidal-shaped islands and ridge structures aligned to the [1 (1) over bar 0] direction. Anisotropic in-plane strain relaxation on (110) is suggested as the formation mechanism of such structures.