Degradation　testing　and　life　testing　are　two　types　of　significant　reliability　tests　for　evaluating　the　lifetime　of　a　product.　When　it　is　difficult　to　obtain　failure　time　data　via　life　testing,　degradation　testing　can　also　be　conducted　to　collect　performance　degradation　data　for　parameters　estimation　and　reliability　assessment.　In　this　paper,　an　optimal　design　method　is　proposed　to　determine　the　number　of　units　allocated　in　degradation　testing　and　life　testing　under　constrains.　Firstly,　the　degradation　characteristic　is　described　by　using　Wiener　process　model,　and　the　reliability　model　and　parameters　estimations　are　derived　both　using　degradation　data　and　lifetime　data.　Secondly,　based　on　V-optimality　criterion,　under　the　constraint　that　test　cost　does　not　exceed　a　predetermined　budget,　the　optimal　design　of　test　number　in　each　test　is　obtained　by　minimizing　the　asymptotic　variance　of　the　maximum　likelihood　estimator,　which　is　the　p-quantile　of　the　lifetime　distribution.　Finally,　a　numerical　example　is　presented　to　illustrate　the　use　of　the　proposed　method　in　practice,　and　show　its　meaningful　in　improving　the　estimation　accuracy.