In computer aided geometric design (CAGD), Bézier-like bases receive more and more considerations as new modeling tools in recent years. But those existing Bézier-like bases are all defined over the rectangular domain. In this paper, we extend the algebraic trigonometric Bézier-like basis of order 4 to the triangular domain. The new basis functions defined over the triangular domain are proved to fulfill non-negativity, partition of unity, symmetry, boundary representation, linear independence and so on. We also prove some properties of the corresponding Bézier-like surfaces. Finally, some applications of the proposed basis are shown. §1 IntroductionIn computer aided geometric design (CAGD), the classical Bernstein-Bézier system defined for polynomial space has become an important tool for free form curve/surface modeling since 1960s. In recent years, the Bézier-like basis defined for the blended spaces has received attention. The most important reason is that Bézier-like bases can exactly represent many analytic curves and surfaces. However the NURBS representations have complicated rational forms. In 1990s, Zhang [14,15] presented the Bézier-like curves, called C-Bézier, for the space Γ =span{1, t, sin t, cos t}. In 2004, Chen and Wang [4] extended them to the general algebraic trigonometric polynomial space. Meanwhile, the properties and applications of the C-Bézier were widely studied in many documents [6][7][8]11,13]. There exists similar theory for both the algebraic trigonometric space and the algebraic hyperbolic space. And many scholars, for example, Fang, Xu and Zhang [5,12,16], unified these two spaces by introducing new parameters, initial functions and complex numbers.The above mentioned papers on Bézier-like curves and surface are all confined in the rectangular domain. However, curves and surfaces modeling over the triangular domain are also important, just like Bernstein-Bézier system [1-3]. Furthermore, Shen and Wang [9,10] have