Local-lag mechanism can eliminate short-term inconsistencies for collaborative virtual environments (CVEs). However, local-lag mechanism increases the response time and deteriorates the task performance of the system when lag is large. This paper first analyzes the effects of local-lag mechanism on task performance in a pilot experiment. We find that the key reason for the task performance deterioration is that subjects do not know the current position of the virtual object controlled by him/her and how long the lag is. Based on this observation, this paper proposes a method named echo, which gives some cues to subjects and makes them perceive these information. Experiment results indicate that the method can improve the task performance significantly. Especially when lag exceeds 600 ms, almost half of subjects cannot finish the task without the help of echo method, but with the help of the echo method all subjects can finish the task fluently.