Water application uniformity is an important performance criterion that must be considered during the design and evaluation of the microirrigation systems. This study was conducted to evaluate the water application uniformity considering field slopes. The uniformity parameters including coefficient of variation (CV), Christiansen’s uniformity coefficient (UCC), distribution uniformity (DU), emitter discharge variation qv(q max) expressed by the difference between the maximum emitter flow rate qmax and the minimum emitter flow rate qmin to qmax, emitter discharge variation qv(qd) expressed by the difference between qmax and qmin to design emitter flow rate qd, emitter discharge variation qv(qd) expressed by the difference between qmax and qmin to average emitter flow rate q(avg), emission uniformity (EU(q avg)) expressed by qmin to qavg, and EU(qd) expressed by qmin to qd. Furthermore, the relationships of CV versus UCC, CV versus DU, CV versus qv(qd), CV versus qv(q max), CV versus qv(q avg), CV versus EU(q avg), and CV versus EU(qd) were also discussed. The results of the study revealed that the field slope does not obviously affect the relationships of CV versus UCC, CV versus qv(q max), and CV versus qv(q avg) for any of the slopes evaluated, which include uphill, zero slope, and downhill. Furthermore, the effect of slope on the relationships of CV versus EU(q avg), CV versus EU(qd), and CV versus qv(qd) was obvious, especially when large downhill slopes with a CV>0.05 were considered. However, the effect of slope on the relationships of CV versus DU was intermediate. Taken together, the results of this study indicated that the UCC, qv(q max), and qv(q avg) should be recommend in addition to CV when evaluating the water application uniformity of the microirrigation systems, regardless of slope, and that qv(qd) and EU(qd) should be recommend when evaluating systems placed in fields with a slope of zero or an uphill slope.